• Journal of Institute of Control, Robotics and Systems
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• v.19 no.3
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• pp.268-274
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• 2013

In this paper, the performance analysis of optics-based sensor node localization using ToF (Time of Flight) scheme is conducted. Generally, the position of the sensor node is calculated on the base station. And the base station scans neighboring sensor nodes with a laser. The laser which is reflected from one sensor node, however, can be reached to the base station at different angles according to the scanning resolution. This means that the error of the reached angle can increase and one node may be recognized as different nodes. Also the power of laser can decrease because the laser signal spread. Thus the sensor node which is located at a long distance from the base station cannot be detected. In order to overcome these problems which can be occurred in localization using ToF, the beam spot, the scanning resolution, the size of reflector and the power of laser at the sensor node were analyzed. It can be expected that the consequence of analysis can be provided in acquisition of accurate position of sensor node and construction of optics-based sensor node localization system.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.11a
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• pp.111-111
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• 2009

In this work, we discuss simulation of surface acoustic wave device using Comsol Multiphysics. The structure SAW device based on piezoelectric thin film aluminum-nitride (AlN) on silicon was simulated. Some parameters of SAW device such as surface velocity, displacement of piezoelectric thin film were evaluated by software. Many modes and shapes of wave are also discussed in this paper. For evaluation physical parameters of AlN piezoelectric layer, the SAW resonator was modeled and simulation results were also compared with experiment results. we simulated arid evaluated the surface Rayleigh wave of AlN thin film on silicon substrate. Results simulation and experiment showed the surface velocity of AlN thin film was about 5200 m/s and shape of surface wave was also displayed. This paper has also proposed as method to study SAW characteristic of piezoelectric thin film and found out measurement values accurately of film such as stiffness matrix, piezoelectric matrix. These values are very important in calculation and design SAW device or MEMS device based on AlN piezoelectric layer.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.11a
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• pp.118-118
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• 2009

Low temperature co-fired ceramic (LTCC) is one of promising materials for MEMS structures because it has very good electrical and mechanical properties as well as possibility of making various three dimensional (3D) structures. In this work, piezoelectric pressure sensors based on hybrid LTCC technology were presented. The LTCC diaphragms with thickness of 400 um were fabricated by laminating 12 green tapes which consist of alumina and glass particle in an organic binder. The piezoelectric sensing layer consists of $Pb(ZrTi)O_3$ (PZT) thin film deposited by RF magnetron sputtering method on between top and bottom Au electrodes. The results showed that the fabrication method is very suitable for pressure sensor applications. The PZT films deposited on LTCC diaphragms were successfully grown and were analyzed by using X-ray diffraction method (XRD) and field emission scanning electron microscope (FESEM).

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.06a
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• pp.195-196
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• 2009

This paper describes the fabrication and characteristics of polycrystalline 3C-SiC thin film diodes for extreme environment applications, in which the this thin film was deposited onto oxidized Si wafers by APCVD using HMDS In this work, the optimized growth temperature and HMDS flow rate were $1,100^{\circ}C$ and 8sccm, respectively. A Schottky diode with a Au, Al/poly 3C-SiC/$SiO_2$/Si(n-type) structure was fabricated and its threshold voltage ($V_d$), breakdown voltage, thickness of depletion layer, and doping concentration ($N_D$) values were measured as 0.84V, over 140V, 61nm, and $2.7{\times}10^{19}cm^2$, respectively. To produce good ohmic contact, Al/3C-SiC were annealed at 300, 400, and $500^{\circ}C$ for 30min under a vacuum of $5.0{\times}10^{-6}$Torr. The obtained p-n junction diode fabricated by poly 3C-SiC had similar characteristics to a single 3C-SiC p-n junction diode.

• Proceedings of the Korean Society of Surveying, Geodesy, Photogrammetry, and Cartography Conference
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• 2006.04a
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• pp.77-81
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• 2006

GPS cannot determine random errors such as multipath and signal cutoff caused by surrounding environment that determines the visibility of satellites and the speed of data creation and transmission is lower than the speed of vehicles, it is difficult to determine accurate dynamic positions. Thus this study purposed to implement a method of deciding the accurate dynamic position of vehicles by combining AHRS (Attitude Heading Reference System) IMU (Initial Measurement Unit) based on low-priced MEMS (Micro Electro Mechanical System) in order to provide the information of attitude, position and speed at a high transmission rate without external help. This study conducted an initialization test to decide dynamic position using AHRS IMU sensor, and derived attitude correction angles of vehicles against time through regression analysis. The roll angle was $y=(A{\times}10^{-6})x^2 -(B{\times}10^{-5})x+Cr{\times}10^{-2}$ and the pitch angle was $y=(A{\times}10^{-6})x^2-(B{\times}10^{-7})x+C{\times}10^{-2}$, each of which was derived from second-degree polynomial regression analysis. It was also found that the heading angle was stabilized with variation less than $1^{\circ}$ after 60 seconds.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.25 no.5
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• pp.366-371
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• 2012

In this paper, fabricated by MEMS uncooled micro-bolometer detector for the study in the infrared sensitivity enhancement. Absorption layer SiOx-Metal series MDTF (metal-dielectric thin film) by high absorption rate and has a high thermal coefficient of resistance, low noise characteristics were implemented. Then MDTF were made in a vacuum deposition method. And MDTF for the analysis of the physical properties of silicon wafers were fabricated, TCR (temperature coefficient of resistance) value was made in order to measure the glass wafer and FT-IR (Fourier Transform Infrared spectroscopy) values were made in order to measure the germanium window. The analyzed results of MDTF -3 [%/K] has more characteristics of the TCR. And 8~12 um wavelength region close to 70% in the absorption characteristic.

• Proceedings of the KIEE Conference
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• 2005.10b
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• pp.264-266
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• 2005

Recently, on-line diagnosis methods through wired and wireless networks are widely adopted in the diagnosis of industrial Electric Facilities, such as generators, transformers and motors. Also smart sensors which includes sensors, signal conditioning circuits and micro-controller in one board are widely studied in the field of condition monitoring. This paper suggests an self-powered system suitable for condition-monitoring smart sensors, which uses parasitic vibrations of the facilities as energy source. First, vibration-driven noise patterns of the electric facilities are presented. And then, an electromagnetic generator which uses mechanical mass-spring vibration resonance are suggested and designed. Finally energy consumption of the presented smart sensor, which consists of MEMS vibration sensors, signal conditioning circuits, a low-power consumption micro-controller, and a ZIGBEE wireless tranceiver, are presented. The usefulness and limits of the presented electromagnetic generators in the field of electric facility monitoring are also suggested.

• IEMEK Journal of Embedded Systems and Applications
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• v.2 no.2
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• pp.76-81
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• 2007

A novel multi-layer type micro gas sensor for $NO_X$ detection was designed and fabricated. Micro platform defined as type II-1 in this article for micro gas sensor was fabricated using the MEMS technology to meet the demanding needs of lower power consumption. Nano composite materials were fabricated with nanosized tin oxide powder and $\underline{m}$ulti-$\underline{w}$all $\underline{c}$arbon $\underline{n}$ano $\underline{t}$ube (MWCNT) to improve sensitivity. We investigated characteristics of fabricated multi-layer type micro gas sensor with $NO_2$ concentration variations at constant 2.2 V. Sensitivity (S) of micro gas sensor were observed to increase from 2.9, to 7.4 and 11.2 as concentrations of $NO_2$ gases increased from 2.4 ppm, to 3.6 ppm and 4.9 ppm. When 2.4 ppm of $NO_2$ gas was applied, response time and recovery time of micro gas sensor were recorded as 101 seconds and 142 seconds, respectively.

• Current Industrial and Technological Trends in Aerospace
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• v.5 no.2
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• pp.58-66
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• 2007

지상, 항공 및 우주를 이동하는 모든 물체는 반드시 자신의 자세를 결정하기 위해서 여러 가지 센서들을 장착하여 그 신호를 이용해서 자동 항법, 유도 및 제어를 수행한다. 이때, 동역학 특성이 빠른 시스템들은 반드시 각속도를 측정할 수 있어야 하는데 이를 해결하는 장비가 자이로인 것이다. 본 논문에서는 다양한 자이로를 소개하며 그 원리와 성능 그리고 적용 분야에 이르기까지 현황을 집중 분석하고 특히 세계적인 자이로 개발업체를 소개하면서 그 업체가 보유하고 있는 제품들을 일부 소개한다. 자이로는 초창기 김벌 시스템을 이용한 관성원리를 적용한 것부터 시작하여 현재는 광학 시스템을 적용한 RLG 및 FOG 자이로가 많은 분야에서 사용되고 있고, 최근 새롭게 부각되어 개발을 시작하고 있는 MEMS 자이로가 있는데 아직 우주 비행체 분야에서는 적용되지 못하고 있다. 그리고, 자이로의 큰 범주로 다루어지지는 않지만 자기력을 이용해서 회전체인 로터와 고정체인 플랫폼 사이에 기계식 접촉이 전혀 없는 새로운 시스템인 ESG 자이로도 일부 상용으로 생산되고 있다. 현재까지는 기계식 자이로의 정밀도 및 안정성이 광학식 자이로보다 우수하여 많이 사용되고 있지만 최근의 개발 추세로 보면 곧 광학식 자이로의 강세가 두드러질 것으로 보인다.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.08a
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• pp.223-223
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• 2011

적외선 감지기로 사용되는 microbolometer 소자재료로 VOx 또는 비정질 Si이 가장 많이 사용된다. 그 중에서 VOx 물질은 온도저항계수 즉, TCR이 높고 감지도가 우수하기 때문에 비냉각 적외선 검출기에 많이 응용된다. Microbolometer 검출기는 그 응답도는 micromachining 공정에 의해 좌우되는 열 고립구조에 의해 좌우된다. 특히 TCR 값이 크고, 열시상수 값이 작을수록 양질의 감지도를 얻을 수 있으므로 재료의 선택 및 공정이 매우 중요하다. 따라서 본 연구에서는 비냉각 적외선 감지소자로 사용되는 VOx 박막을 DC Sputtering을 사용하여 증착하였으며, 그 특성을 조사하였다. MEMS 공정에 의한 센서의 제작은 적외선을 흡수하여 저항변화를 읽어내어 판독하는 Readout IC(ROIC) 위에 행해진다. Monolithic 공정에 의해 이러한 ROIC 위에서 공정이 동시에 행해지므로 공정온도는 매우 중요한 요소로 작용한다. 따라서 증착된 VOx 박막의 열처리 효과를 연구하였다. 열처리 온도는 $250^{\circ}{\sim}420^{\circ}C$, 열처리 시간은 20~80 min 까지 변화시켰다. 갓 증착된 VOx 박막의 저항은 약 200 $k{\Omega}$이였으며, TCR은 -1.5%/$^{\circ}C$로 나타났다. 열처리 온도가 증가함에 따라 TCR 값은 증가하였으며, 열처리 시간이 증가할수록 역시 TCR 값이 증가하는 경향을 보였다. 열처리 온도 320$^{\circ}C$, 열처리 시간 40 min에서 TCR 값은 약 -2%/$^{\circ}C$의 값을 얻을 수 있었다. 이러한 성능의 VOx 박막을 이용하여 비냉각형 microbolometer 검출소자를 열변형없이 공정을 수행할 수 있을 것으로 기대한다.