• Journal of the Korea Institute of Information and Communication Engineering
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• v.7 no.2
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• pp.250-254
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• 2003

A film bulk acoustic resonator (FBAR) device for 2 GHz radio frequency (RF) bandpass filter application is presented. This FBAR device consists of an aluminum nitride (AlN) film sandwiched between top(Al) and bottom(Au) electrodes and an acoustic multilayer reflector of a silicon dioxide/tungsten (SiO2/W). The A/N film deposited using a RF sputtering was observed to have small columnar grains with a strongly preferred orientation towards c axis. In addition to a high quality factor (4300), a large return loss of 37.19 dB was obtained.

• Transactions on Electrical and Electronic Materials
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• v.15 no.2
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• pp.91-95
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• 2014

This paper presents the structure and process technology of simple and low-cost wafer-level packaging (WLP) for thin film radio frequency (RF) devices. Low-cost practical micromachining processes were proposed as an alternative to high-cost processes, such as silicon deep reactive ion etching (DRIE) or electro-plating, in order to reduce the fabrication cost. Gold (Au)/Tin (Sn) alloy was utilized as the solder material for bonding and hermetic sealing. The small size fabricated WLP of $1.04{\times}1.04{\times}0.4mm^3$ had an average shear strength of 10.425 $kg/mm^2$, and the leakage rate of all chips was lower than $1.2{\times}10^{-5}$ atm.cc/sec. These results met Military Standards 883F (MIL-STD-883F). As the newly proposed WLP structure is simple, and its process technology is inexpensive, the fabricated WLP is a good candidate for thin film type RF devices.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.57 no.10
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• pp.1802-1806
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• 2008

Dye-sensitized solar cell (DSC) based on some advantages such as transparency, cheap materials and anti-sensibility for an anlge of incidence has been expected to capture most of solar cell market in the near future. To practical use of DSC, researches on high efficiency as well as upscaling are necessary. In this study, we tried to insert the grid electrode in DSC and scribe transparent conducting oxide (TCO) using Nd:YAG laser. The grid electrode makes the electron movement improved and diffusional movement minimized. Consequently, the efficiency of DSC was increased by reducing electron loss and the surface resistance of TCO. The grid electrode was made using Ag target by radio frequency sputtering. And the scribed surface was confirmed by taking a scanning electron microscopy photos. As the result, grid cell had improved photocurrent and fill factor as compared with the conventional cell. And the efficiency was increased about 1% by enhanced photocurrent and fill factor.

• 한국신재생에너지학회:학술대회논문집
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• 2007.06a
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• pp.257-260
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• 2007

In this study, $CuInSe_{2}$ (CISe) and $CuInZnSe_{2}$ (CIZSe) thin films were prepared on Corning 1737 glass by radio frequency (RF) magnetron sputtering from binary chalcogenide mixed powder targets. The targets were initially prepared by mixing appropriate weights of CuSe, InSe powder and various ZnSe contents. From the film bulk analysis result, it is observed that Zn concentration in the films increases proportionally with the addition of ZnSe in the sputtering targets. Under optimized conditions, CISe and CIZSe thin films grow as a chalcopyrite structure with strong (112), (220/204) and (312/116) reflections. Films are found to exhibit a high absorption coefficient of $10^{4}$ $cm^{-1}$. An increasing of optical band gap from 1.0 eV (CISe) to 1.25 eV (CIZSe) is found to be proportional with an increasing of Zn concentration as expected. All films have a p-type semiconductor characteristic with a carrier concentration in the order of 1014 $cm^{-3}$, a mobility about $10^{1}$ $cm^{2{\cdot}-1}{\cdot}s^{-1}$ and a resistivity at the range of $10^{2}-10^{6}$ W${\cdot}$m.

• Journal of Korean Institute of Industrial Engineers
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• v.33 no.4
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• pp.430-438
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• 2007

In the current RFID (Radio Frequency IDentification) middleware systems based on the EPCglobal standard, the tag data received by multiple readers are processed sequentially in FIFO (First In First Out) order. Considering the priority of RFID reader makes the RFID system more flexible and improve the data transaction throughput in the service environment where important tag data with high priority for a specific reader. In this study, we propose a new RFID middleware system architecture supporting priority service with the Buffer Management Component. Our proposals are compliant with the EPCglobal ALE (Application Level Events) standard interface for middleware systems and their clients. To verify the efficiency of this proposed system, simulation is used for evaluation.

• Journal of Powder Materials
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• v.18 no.2
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• pp.135-140
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• 2011

The RFID (Radio-Frequency Identification) is an automatic identification method, relying on storing and remotely retrieving data using devices called RFID tags or transponders. Some RFID tags have been used in severe environment of temperature ranged from $200^{\circ}C$ to $250^{\circ}C$ for a long time and may cause serious problems such as signal error, short life cycle and explosion. Conventionally, the RFID tags for high temperature applications consisted of Fe-alloy housing part, ceramic powder and RFID sensor. However, it has disadvantage of heavy weight, signal noise and heat shield capability. In this study, we newly applied the aluminum porous materials fabricated by polymer leaching process into RFID tags in order to improve heat shielding ability, and compared the properties of RFID tag inserted by aluminum porous with the conventional one.

• Proceedings of the KAIS Fall Conference
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• 2011.12b
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• pp.529-532
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• 2011

Recently research efforts for ubiquitous technology that includes RFID(Radio Frequency Deification and sensor networks are conducted very actively The architectural framework of the USN sensor network discovery service. The survey of the USN technology is conducted on four technological visions that contain USN system technology USN networking technology and USN middleware along with the service platform, With respect to each technological division domestic and worldwide leading research projects are primarily explored with their technical features and research projects are primarily explored with their technical features and research outputs. Boasted on the result of the survey we establish a USN software model that includes data sensing, sensor data storage sensor data storage sensor data naming and sensor feed name service. This main objective of this model is to provide a reference model for the facilitation of USN application developments.

• Journal of the Korean Magnetic Resonance Society
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• v.7 no.1
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• pp.25-36
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• 2003

The performance of radio frequency (RF) coils, used in MRI units, is determined by the image uniformity and the signal-to-noise ratio (SNR). Birdcage and surface coils are commonly used. A birdcage coil provides a good image uniformity while a surface coil produces a high SNR. In this study, therefore, a staircase coil was designed from a standard version of a birdcage coil, with some structural changes to increase SNR while maintaining image uniformity. In phantom experiments, the improvement of the image to uniformity and the SNR increase of the staircase coil compared with the values for the birdcage coil were about 3.5% and 35%, respectively. In clinical experiment, the SNR increase of the staircase coil, compared with the value for the birdcage coil was about 40% in bone, muscle and blood-vessel tissues. These results show that the performance of the staircase coil was very improved over the standard birdcage coil in terms of SNR, and that image uniformity was maintained. Therefore, the staircase coil designed by this study should be useful in experimental and clinical l.5T MRI systems, and this coil offers an alternative method of quadrature detection.

• Applied Science and Convergence Technology
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• v.25 no.4
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• pp.73-76
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• 2016

Multi-layer films of $SiN_x/SiO_x$/InSnO with anti-reflective effect were grown by new-concept plasma enhanced chemical vapor deposition system (PECVD) with hybrid plasma source (HPS). Anti-reflective effect of $SiN_x/SiO_x$/InSnO was investigated as a function of ratio of $SiN_x$ and $SiO_x$ thickness. Multi-layers deposited by PECVD with HPS represents the enhancement of anti-reflective effect with high transmittance, comparing to the layers by conventional radio frequency (RF) sputtering system. This change is strongly related to the optical and physical properties of each layer, such as refractive index, composition, film density, and surface roughness depending on the deposition system.

• The Journal of the Korea institute of electronic communication sciences
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• v.6 no.2
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• pp.304-311
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• 2011

Recently, tourism is one of future promising industries having high developing possibilities, so many countries have developed tour resources and tried to attract foreign tourists using the resources. Many researches and attempts have tried to apply for tourism using various technologies such as GPS and RFID. However, the applying areas have been highly restricted to the technology providing contents on the spot for independent tourists. Therefore, this paper designed and implemented "Intelligent Tour Guide System (ITGS)" using GPS and ZigBee. The ITGS is for group tourists, and provides various functions for enjoying their tours in limited schedules.