• Publications of The Korean Astronomical Society
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• v.13 no.1 s.14
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• pp.39-54
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• 1998

We have developed solar observational system in the department of Astronomy & Space Sciences of KyungHee University, in order to monitor solar activities and construct solar database for space weather forecasting at maximum of 23rd solar cycle, as well as an solar education and exercise for undergraduate students. Our solar observational system consists of the full disk monitoring system and the regional observation system for H a fine structure. Full disk monitoring system is made of an energy rejection filter, 16cm refractor, video CCD camera and monitor. Monitored data are recorded to VHS video tape and analog output of video CCD can be captured as digital images by the computer with video graphic card. Another system for regional observation of the sun is made of energy rejection filter, 21cm Schmidt-Cassegrain reflector, H a filter with 1.6A pass band width and $375\times242$ CCD camera. We can observe H a fine structure in active regions of solar disk and solar limb, by using this system. We have carried out intense solar observations for a test of our system. It is found that Quality of our H a image is as good as that of solar images provided by Space Environmental Center. In this paper, we introduce the basic characteristics of the KyungHee Solar Observation System and result of our solar observations. We hope that our data should be used for space weather forecasting with domestic data of RRL(Radio Research Laboratory) and SOFT(SOlar Flare Telescope).

• Journal of Sensor Science and Technology
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• v.32 no.6
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• pp.425-431
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• 2023

An asymmetric metal-semiconductor-metal Al_0.24Ga_0.76N ultraviolet (UV) sensor was fabricated, and the effects of local Joule heating were investigated. After dielectric breakdown, the current density under a reverse bias of 2.0 V was 1.1×10^-9 A/cm², significantly lower than 1.2×10^-8 A/cm² before dielectric breakdown; moreover, the Schottky behavior of the Ti/Al/Ni/Au electrode changed to ohmic behavior under forward bias. The UV-to-visible rejection ratio (UVRR) under a reverse bias of 7.0 V before dielectric breakdown was 87; however, this UVRR significantly increased to 578, in addition to providing highly reliable responsivity. Transmission electron microscopy revealed interdiffusion between adjacent layers, with nitrogen vacancies possibly formed owing to local Joule heating at the AlGaN/Ti/Al/Ni/Au interfaces. X-ray photoelectron microscopy results revealed decreases in the peak intensities of the O 1s binding energies associated with the Ga-O bond and OH-, which act as electron-trapping states on the AlGaN surface. The reduction in dark current owing to the proposed local heating method is expected to increase the sensing performance of UV optoelectronic integrated devices, such as active-pixel UV image sensors.

• ETRI Journal
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• v.26 no.3
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• pp.229-240
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• 2004

This paper reports on our development of a dual-mode transceiver for a CMOS high-rate Bluetooth system-onchip solution. The transceiver includes most of the radio building blocks such as an active complex filter, a Gaussian frequency shift keying (GFSK) demodulator, a variable gain amplifier (VGA), a dc offset cancellation circuit, a quadrature local oscillator (LO) generator, and an RF front-end. It is designed for both the normal-rate Bluetooth with an instantaneous bit rate of 1 Mb/s and the high-rate Bluetooth of up to 12 Mb/s. The receiver employs a dualconversion combined with a baseband dual-path architecture for resolving many problems such as flicker noise, dc offset, and power consumption of the dual-mode system. The transceiver requires none of the external image-rejection and intermediate frequency (IF) channel filters by using an LO of 1.6 GHz and the fifth order onchip filters. The chip is fabricated on a $6.5-mm^{2}$ die using a standard $0.25-{\mu}m$ CMOS technology. Experimental results show an in-band image-rejection ratio of 40 dB, an IIP3 of -5 dBm, and a sensitivity of -77 dBm for the Bluetooth mode when the losses from the external components are compensated. It consumes 42 mA in receive ${\pi}/4-diffrential$ quadrature phase-shift keying $({\pi}/4-DQPSK)$ mode of 8 Mb/s, 35 mA in receive GFSK mode of 1 Mb/s, and 32 mA in transmit mode from a 2.5-V supply. These results indicate that the architecture and circuits are adaptable to the implementation of a low-cost, multi-mode, high-speed wireless personal area network.

• 제어로봇시스템학회:학술대회논문집
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• 1997.10a
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• pp.365-370
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• 1997

In this paper we suggest a development of surface defect inspection algorithms for cold mill strip using tree structure. The defects which exist in a surface of cold mill strip have a scattering or singular distribution. This paper consists of preprocessing, feature extraction and defect classification. By preprocessing, the binarized defect image is achieved. In this procedure, Top-hit transform, adaptive thresholding, thinning and noise rejection are used. Especially, Top-hit transform using local min/max operation diminishes the effect of bad lighting. In feature extraction, geometric, moment, co-occurrence matrix, histogram-ratio features are calculated. The histogram-ratio feature is taken from the gray-level image. For the defect classification, we suggest a tree structure of which nodes are multilayer neural network clasifiers. The proposed algorithm reduced error rate comparing to one stage structure.

• JSTS:Journal of Semiconductor Technology and Science
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• v.4 no.3
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• pp.182-188
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• 2004

We demonstrate a $2.1\;{\times}\;1.0\;{\times}\;0.1cm^3$ sized compact transmitter using LTCC System-in-Package (SiP) technology for 60GHz-band wireless communication applications. For low-attenuation characteristics and resonance suppression of the SiP, we have proposed and demonstrated a coplanar double wire-bond transition and novel CPW-to-stripline transition integrating air-cavities as well as novel air-cavities embedded CPW line. The fabricated transmitter achieves an output of 13dBm at a RF frequency of 62GHz, an IF frequency of 2.4GHz, and a LO frequency of 59.6GHz. The up-conversion gain is 11dB, while the LO signal is suppressed with the image rejection mixer below -21.4dBc, and the image and spurious signals are also suppressed below -31dBc.

• 제어로봇시스템학회:학술대회논문집
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• 1996.10b
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• pp.1332-1335
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• 1996

It is very important to predict the future position for the heavy vehicle with evasive maneuvering. In this paper, we considered for the manual image tracking system. The vehicle images are received from gyro stabilized mirror system, pass through the optical lens, processed, and displayed on the TV monitor. The operator try to lay the reticle to the center of vehicle image. When the vehicle is moving, the mirror platform (actually the line of sight) should follow the vehicle and the angular rate information is picked up from the mirror stabilized system. This rate signal should be used to predict the future vehicle position. The problem is that the visual system of the human operator is in the closed loop system. The rate signals are disturbed by the operator. In addition, there are some non linearities concerned with the control handle bar and the servo control system. The proposed Kalman filter, combined with some modifications for operator disturbance rejection, improved the predication of the future vehicle position when compared with the conventional passive filter used.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.27 no.4C
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• pp.365-370
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• 2002

In this paper external image multi-processing digital signal the transmit is the possibility of doing system with the PCI the design. The bottle-neck which it follows in transmission ratio limit of the CPU and the circumference machineries and tools against the image data which with the improve one thing becomes the processing with the real-time efficiently the transmit and the control is the possibility of doing structure the proposed. The also with the resource amount used 13% reduced which PCI fast data transfer and DMA function. The designed is operation verification against the function and the timing which use Max+plus II.

• Proceedings of the IEEK Conference
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• 2007.07a
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• pp.375-376
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• 2007

This paper proposes an algorithm for rejecting mismatched points (known as outliers). The proposed algorithm identifies and rejects outliers in image pairs obtained under automobile-like motions which consist of two translations and one rotation. The camera rotation is approximated to the image shift by assuming that the narrow field of lens is used. The voting method estimates the focus of expansion (FOE) while shifting one of the images. Using the properties of the FOE, the outliers are rejected while most of the inliers are retained.

• Journal of Sensor Science and Technology
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• v.17 no.5
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• pp.346-349
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• 2008

A metal-semiconductor-metal (MSM) ultraviolet (UV) photodetector (PD) is proposed as an effective UV sensing device for integration with a GaN n-channel MISFET on auto-doped p-type GaN grown on a silicon substrate. Due to the high hole barrier of the metal-p-GaN contact, the dark current density of the fabricated MSM PD was less than $3\;nA/cm^2$ at a bias of up to 5 V. Meanwhile, the UV/visible rejection ratio was 400 and the cutoff wavelength of the spectral responsivity was 365 nm. However, the UV/visible ratio was limited by the sub-bandgap response, which was attributed to defectrelated deep traps in the p-GaN layer of the MSM PD. In conclusion, an MSM PD has a high process compatibility with the n-channel GaN Schottky barrier MISFET fabrication process and epitaxy on a silicon substrate.

• Proceedings of the KIEE Conference
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• 2003.11c
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• pp.894-897
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• 2003

Recently, the rapid growth of mobile radio system has led to an increasing demand of low-cost high performance communication IC's. In this paper, we have designed RF front end for wireless LAN receiver employ zero-IF architecture. A low-noise amplifier (LNA) and double-balanced mixer is included in a front end. The zero-IF architecture is easy to integrate and good for low power consumption, so that is coincided to requirement of wireless LAN. But the zero-IF architecture has a serious problem of large offset. Image-reject mixer is a good structure to solve offset problem. Using offset compensation circuit is good structure, too. The front end is implemented in 0.25 ${\mu}m$ CMOS technology. The front end has a noise figure of 5.6 dB, a power consumption of 16 mW and total gain of 22 dB.