• 한국정보통신학회:학술대회논문집
• /
• 한국해양정보통신학회 2000년도 춘계종합학술대회
• /
• pp.465-469
• /
• 2000

광대역 무선 디지털 통신 시스템용 파이프라인 적응 결정귀환 등화기 (pipelined adaptive decision- feedback equalizer; PADFE)를 0.25-$\mu\textrm{m}$ CMOS 공정을 사용하여 full custom 단일 칩으로 설계하였다. ADFE의 동작속도를 향상시키기 위해 DLMS (delayed least-mean-square)을 적용한 2-stage 파이프라인 구조로 설계하였다. PADFE의 필터와 계수갱신 블록 등 모든 연산을 redundant binary (RB) 수치계로 처리하였으며, 2의 보수 수치계를 사용하는 기존의 방식에 비해 연산량의 감소와 동작속도의 향상이 얻어졌으며, 또한 전체적인 구조의 단순화에 의해 VLSI 구현이 용이하다는 장점을 갖는다. COSSAP을 이용한 알고리듬 레벨 시뮬레이션을 통해 파이프라인 stage 수, 필터 tap 수, 계수 및 내부 비트 수 등의 설계 파라메터 결정과 bit error rate (BER), 수렴속도 등을 분석하였다. 설계된 PADFE는 약 205,000개의 트랜지스터로 구성되며, 코어의 면적은 1.96$\times$1.35-mm$^{2}$이다. 시뮬레이션 결과, 2.5-V 전원전압에서 200-MHz의 클록 주파수로 안전하게 동작할 수 있을 것으로 예상되며, 평균 전력소모는 약 890-mW이다.

• 한국정보통신학회논문지
• /
• 제6권2호
• /
• pp.221-227
• /
• 2002

본 논문에서는 3GPP(3rd Generation Partnership Project) 비동기(asynchronous) WCDMA(Wide-band CDMA) 시스템에 HIC(Hybrid Interference Cancellation) 기법의 MUD (Multi-User Detector)를 적용하여 Rayleigh 페이딩 채널에서 BER (Bit Error Rate) 성능을 컴퓨터 시뮬레이션을 통해 구하였다. 이 결과를 감산형 간섭제거기법의 대표적인 방식인 SIC(Successive Interference Cancellation) 기법, PIC(Parallel Interference Cancellation) 기법의 BER(Bit Error Rate) 성능과 비교 분석하였다. 분석한 결과, 전송률이 높은 사용자들은 PIC 기법이나 HIC 기법을 사용하여 간섭을 제거하는 것이 효과적이고, 전송률 이 낮은 사용자들은 SIC 기법이나 HIC 기법을 사용하는 게 효과적이라는 것을 알 수 있었다. 또한, 전송률에 의존하지 않고 모든 사용자의 성능을 고루 만족시키기 위해서는 HIC 구조를 사용하는 것이 효과적이었다. 그 이유로서는 페이딩 채널상의 이유에서 또는 원하는 서비스를 만족시키기 위해서 사용자가 전력을 높일지라도 HIC 기법에서는 전단에 사용하는 SIC에 의해 전력이 낮은 사용자들의 성능을 보장해주고 후단에 사용하는 PIC에 의해 SIC 과정에서 전력이 센 사용자가 받는, 전력이 약한 사용자로부터의 간섭이 효과적으로 제거되기 때문이다.

• 한국인터넷방송통신학회논문지
• /
• 제19권6호
• /
• pp.57-63
• /
• 2019

EMI 차폐막의 높이가 회로에 어떤 영향을 끼치는지를 S파라미터를 통해 분석하였다. S파라미터 중에서 회로의 기능에 끼치는 영향을 판단할 수 있는 요소로서 S11, S21, S22, S31이 있다. 시뮬레이션은 그래파이트와 페라이트로 이루어진 차폐막을 이용하였고, 주파수는 100 MHz ~ 1 GHz에서 진행하였다. 차폐막의 높이가 증가함에 따라 S21값이 0 dB에 점점 가까워지는 모습을 보였다. 또한 SE(Shielding Effectiveness)값은 특정한 주파수 대역에서만 절연층의 두께에 따른 차폐성능의 향상을 확인할 수 있었다. 이산화규소(Silicon dioxide)의 두께가 가장 두꺼운 800 um 경우를 기준으로 FG(Ferrite-Graphite) 구조는 100 MHz ~ 300 MHz의 좁은 주파수 대역에서 평균 -1 dB를 보이며 -2 dB의 평균을 보이는 GF(Graphite-Ferrite)보다 뛰어난 효율을 보인다. GF 구조는 높은 효율을 보이지는 못하지만 넓은 범위에서 흔들리는 FG 구조보다 100 MHz ~ 1 GHz의 주파수 대역에서 -3 dB의 평균적인 성능을 보인다. 즉, FG 구조와 GF 구조는 트레이드-오프(trade-off)의 구조를 갖는다. 따라서 용도에 따라 적절한 구조를 선택해야 한다.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 2008년도 추계학술대회 논문집 Vol.21
• /
• pp.50-50
• /
• 2008

ZnO has been extensively studied for optoelectronic applications such as blue and ultraviolet (UV) light emitters and detectors, because it has a wide band gap (3.37 eV) anda large exciton binding energy of ~60 meV over GaN (~26 meV). However, the fabrication of the light emitting devices using ZnO homojunctions is suffered from the lack of reproducibility of the p-type ZnO with high hall concentration and mobility. Thus, the ZnO-based p-n heterojunction light emitting diode (LED) using p-Si and p-GaN would be expected to exhibit stable device performance compared to the homojunction LED. The n-ZnO/p-GaN heterostructure is a good candidate for ZnO-based heterojunction LEDs because of their similar physical properties and the reproducibleavailability of p-type GaN. Especially, the reduced lattice mismatch (~1.8 %) and similar crystal structure result in the advantage of acquiring high performance LED devices with low defect density. However, the electroluminescence (EL) of the device using n-ZnO/p-GaN heterojunctions shows the blue and greenish emissions, which are attributed to the emission from the p-GaN and deep-level defects. In this work, the n-ZnO:Ga/p-GaN:Mg heterojunction light emitting diodes (LEDs) were fabricated at different growth temperatures and carrier concentrations in the n-type region. The effects of the growth temperature and carrier concentration on the electrical and emission properties were investigated. The I-V and the EL results showed that the device performance of the heterostructure LEDs, such as turn-on voltage and true ultraviolet emission, developed through the insertion of a thin intrinsic layer between n-ZnO:Ga and p-GaN:Mg. This observation was attributed to a lowering of the energy barriers for the supply of electrons and holes into intrinsic ZnO, and recombination in the intrinsic ZnO with the absence of deep level emission.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 2008년도 추계학술대회 논문집 Vol.21
• /
• pp.145-145
• /
• 2008

High-k materials have been paid much more attention for their characteristics with high permittivity to reduce the leakage current through the scaled gate oxide. Among the high-k materials, $ZrO_2$ is one of the most attractive ones combing such favorable properties as a high dielectric constant (k= 20 ~ 25), wide band gap (5 ~ 7 eV) as well as a close thermal expansion coefficient with Si that results in good thermal stability of the $ZrO_2$/Si structure. During the etching process, plasma etching has been widely used to define fine-line patterns, selectively remove materials over topography, planarize surfaces, and trip photoresist. About the high-k materials etching, the relation between the etch characteristics of high-k dielectric materials and plasma properties is required to be studied more to match standard processing procedure with low damaged removal process. Among several etching techniques, we chose the inductively coupled plasma (ICP) for high-density plasma, easy control of ion energy and flux, low ownership and simple structure. And the $BCl_3$ was included in the gas due to the effective extraction of oxygen in the form of $BCl_xO_y$ compounds. During the etching process, the wafer surface temperature is an important parameter, until now, there is less study on temperature parameter. In this study, the etch mechanism of $ZrO_2$ thin film was investigated in function of $Cl_2$ addition to $BCl_3$/Ar gas mixture ratio, RF power and DC-bias power based on substrate temperature increased from $10^{\circ}C$ to $80^{\circ}C$. The variations of relative volume densities for the particles were measured with optical emission spectroscopy (OES). The surface imagination was measured by scanning emission spectroscope (SEM). The chemical state of film was investigated using energy dispersive X-ray (EDX).

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 2008년도 추계학술대회 논문집 Vol.21
• /
• pp.399-399
• /
• 2008

Synthesis and characterization of ZnO structure such as nanowires, nanorods, nanotube, nanowall, etc. have been studied to multifunctional application such as optical, nanoscale electronic and chemical devices because it has a room-temperature wide band gap of 3.37eV, large exiton binding energy(60meV) and various properties. Various synthesis methods including chemical vapor deposition (CVD), physical vapor deposition, electrochemical deposition, micro-emulsion, and hydrothermal approach have been reported to fabricate various kinds of ZnO nanostructures. But some of these synthesis methods are expensive and difficult of mass production. Wet chemical method has several advantage such as simple process, mass production, low temperature process, and low cost. In the present work, ZnO nanorods are deposited on ITO/glass substrate by simple wet chemical method. The process is perfomed by two steps. One-step is deposition of ZnO seeds and two-step is growth of ZnO nanorods on substrates. In order to form ZnO seeds on substrates, mixture solution of Zn acetate and Methanol was prepared.(one-step) Seed layers were deposited for control of morpholgy of ZnO seed layers by spin coating process because ZnO seeds is deposited uniformly by centrifugal force of spin coating. The seed-deposited samples were pre-annealed for 30min at $180^{\circ}C$ to enhance adhesion and crystallinnity of ZnO seed layer on substrate. Vertically well-aligned ZnO nanorods were grown by the "dipping-and-holding" process of the substrates into the mixture solution consisting of the mixture solution of DI water, Zinc nitrate and hexamethylenetetramine for 4 hours at $90^{\circ}C$.(two-step) It was found that density and morphology of ZnO nanorods were controlled by manipulation of ZnO seeds through rpm of spin coating. The morphology, crystallinity, optical properties of the grown ZnO nanostructures were carried out by field-emission scanning electron microscopy, high-resolution electron microscopy, photoluminescence, respectively. We are convinced that this method is complementing problems of main techniques of existing reports.

• 천문학회지
• /
• 제47권6호
• /
• pp.235-253
• /
• 2014

Intensity interferometry, based on the Hanbury Brown-Twiss effect, is a simple and inexpensive method for optical interferometry at microarcsecond angular resolutions; its use in astronomy was abandoned in the 1970s because of low sensitivity. Motivated by recent technical developments, we argue that the sensitivity of large modern intensity interferometers can be improved by factors up to approximately 25 000, corresponding to 11 photometric magnitudes, compared to the pioneering Narrabri Stellar Interferometer. This is made possible by (i) using avalanche photodiodes (APD) as light detectors, (ii) distributing the light received from the source over multiple independent spectral channels, and (iii) use of arrays composed of multiple large light collectors. Our approach permits the construction of large (with baselines ranging from few kilometers to intercontinental distances) optical interferometers at the cost of (very) long-baseline radio interferometers. Realistic intensity interferometer designs are able to achieve limiting R-band magnitudes as good as $m_R{\approx}14$, sufficient for spatially resolved observations of main-sequence O-type stars in the Magellanic Clouds. Multi-channel intensity interferometers can address a wide variety of science cases: (i) linear radii, effective temperatures, and luminosities of stars, via direct measurements of stellar angular sizes; (ii) mass-radius relationships of compact stellar remnants, via direct measurements of the angular sizes of white dwarfs; (iii) stellar rotation, via observations of rotation flattening and surface gravity darkening; (iv) stellar convection and the interaction of stellar photospheres and magnetic fields, via observations of dark and bright starspots; (v) the structure and evolution of multiple stars, via mapping of the companion stars and of accretion flows in interacting binaries; (vi) direct measurements of interstellar distances, derived from angular diameters of stars or via the interferometric Baade-Wesselink method; (vii) the physics of gas accretion onto supermassive black holes, via resolved observations of the central engines of luminous active galactic nuclei; and (viii) calibration of amplitude interferometers by providing a sample of calibrator stars.

• 대한후두음성언어의학회지
• /
• 제17권2호
• /
• pp.98-102
• /
• 2006

Background and Objectives : Voice onset time(VOT) is defined as the time interval from oral release of a stop consonant to the onset of glottal pulsing in the following vowel. VOT is a temporal characteristics of stop consonants that reflects the complex timing of glottal articulation relative to supraglottal articulation. Stop consonants are characterized by creation of a pressure difference across a complete occlusion in the vocal tract, followed by a sudden release 'burst' due to opening that occlusion. The objects of this study is to evaluate a usefulness of voice onset time in the assessment of voice disorderd patients. Subjects : Subjects were 20 adults with normal voice and with benign laryngeal disorders. Subjects with voice disorders represented the following vocal pathologies : vocal polyp, vocal nodule, Reinke's edema and unilateral vocal fold paralysis(UVFP). Control subjects were matched for age (21-40 yews old) and sex(male) with the voice disorders subjects and had normal vocal qualities with no history of voice disorders. Methods : Each voice-disordered and matched control subject read the test passages containing three types of Korean bilabial consonants. VOT measures were made for the initial $/p/p^h/\;and\;/p'/$. VOT was measured using acoustic waveform or wide band spectrogram. Results : For each voiceless stop consonants, there was a significant difference in VOT between the voice disordered and normal subjects. The mean VOTs of the lax stops in UVFP was significantly shorter than those of control subjects in the UVFP. The mean VOTs of the aspirated stops in the vocal polyp and nodule were longer than those of control subjects, but not significant. The mean VOTs of the glottalized in voice disordered groups were longer than those of control subjects, and significant statistically in the UVFP. Conclusions : VOT may be a clinically useful acoustic parameter in the assessment of voice disordered patients, especially in the unilateral vocal fold paralysis.

• 한국해양학회지:바다
• /
• 제3권3호
• /
• pp.158-164
• /
• 1998

광대역 주파수변조(wide-band FM) 선호를 음원으로 사용하는 Chirp sonar 시스템을 이용하여 획득한 음향반사 자료의 통계학적 처리를 통하여 해저면을 분류하였다. 음향학적 분류변수로서 Chirp 자료의 K-L(Karhunen-Lo$\grave{e}$ve) 변환을 이용하여 계산된 유사도 지수(similarity index)를 고안하였다. 유사도 지수는 근접한 트레이스 자료들에 포함된 공통된 반사신호성분의 양을 지시하므로 해저면 퇴적물의 성분에 따른 음향학적 거침도를 반영한다고 할 수 있다. 유사도 지수는 0에서 1사이의 값을 가지며, 각기 다른 퇴적상을 나타내는 지점에서 획득된 Chirp 자료를 처리한 결과, 퇴적물의 성분이 균질할수록, 입자의 크기가 작을수록, 그리고 연한 퇴적층일수록 증가하는 것을 관측할 수 있었다. 실제의 응용 예로서 제주도 성산포 해역을 이 방법으로 분류하였으며, 그 결과를 검증하기 위해 동일해역에서 획득된 side-scan sonar 자료 및 퇴적물로부터 해석된 해저면의 퇴적상과 비교하였다. 그 결과 음향자료의 유사도 지수에 의해 분류된 해저면은 실제의 퇴적상을 매우 잘 반영할 뿐만 아니라 퇴적물 성분의 특성에 따른 음향반응을 더욱 세밀히 나타내었다. 그러므로 이러한 방법은 음향자료로부터 직접 해저면을 분류하는 지질음향 모델링으로서 매우 효과적이다.

• 한국진공학회:학술대회논문집
• /
• 한국진공학회 1999년도 제17회 학술발표회 논문개요집
• /
• pp.62-62
• /
• 1999

Carbon based materials have many attractive properties such as a wide band gap, a low electron affinity, and a high chemical and mechanical stability. Therefore, researches on the carbon-based materials as field emitters have been drawn extensively to enhance the field emission properties. Especially, diamond gives high current density, high current stability high thermal conductivity durable for high temperature operation, and low field emission behaviors, Among these properties understanding the origin of low field emission is a key factor for the application of diamond to a filed emitter and the verification of the emission site and its distribution of diamond is helpful to clarify the origin of low field emission from diamond There have been many investigations on the origin of low field emission behavior of diamond crystal or chemical vapor deposition (CVD) diamond films that is intentionally doped or not. However, the origin of the low field emission behavior and the consequent field emission mechanism is still not converged and those may be different between diamond crystal and CVD diamond films as well as the diamond that is doped or not. In addition, there have been no systematic studies on the dependence of nondiamond carbon on the spatial distribution of emission sites and its uniformity. Thus, clarifying a possible mechanism for the low field emission covering the diamond with various properties might be indeed a difficult work. On the other hand, it is believed that electron emission mechanisms of diamond are closely related to the emission sites and its distributions. In this context, it will be helpful to compare the spatial distribution of emission sites and field emission properties of the diamond films prepared by systematic variations of structural property. In this study, we have focused on an understanding of the field emission variations of structural property. In this study, we have focused on an understanding of the field emission mechanism for the CVD grown undoped polycrystalline diamond films with significantly different structural properties. The structural properties of the films were systematically modified by varying the CH4/H2 ratio and/or applying positive substrate bias examined. It was confirmed from the present study that the field emission characteristics are strongly dependent on the nondiamond carbon contents of the undoped polycrystalline diamond films, and a possible field emission mechanism for the undoped polycrystalline diamond films is suggested.