• Proceedings of the KIEE Conference
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• 1997.11a
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• pp.649-652
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• 1997

The method for the calaulation of the input impedanc of cavity with water is proposed in this paper the electric field and input impedance are calaulated for the water with high conductivity to verify this method. And the electric field and RCS (radar cross section) is calculated when the plane wave scattered by high permitivity and low conductivity material. The calculated results are compared with exact solution. Then this method is compared with the conventional method.

• Electronics and Telecommunications Trends
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• v.32 no.6
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• pp.66-72
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• 2017

The frequency range of a radio wave is from 3kHz to 300GHz, and radio technologies use this range to improve the quality of human lives. Radio technologies have entered a new phase of communication. The core infrastructure used as the basis for technologies leading the fourth industrial evolution, such as artificial intelligence, the Internet of Things, autonomous cars/drones, augmented reality, robots, and remote medical diagnoses, is the 5G network. The 5G network enables transmitting and receiving large amounts of data at very high speed. In particular, application technologies with artificial intelligence have been studied, including radar, wireless charging, electromagnetic devices and their effects on humans, EMI/EMC, and microwave imaging. In this study, we present a future radio technology that is needed to prepare for the upcoming industrial revolution and digital transformation.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.30 no.1
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• pp.87-95
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• 2016

Recently, the interests of the precise localization are rapidly increasing, which are linked to IoT(Internet of Things) sensors. The precise localization in indoor environment can be utilized in navigation, security, anti-collision, and various location based services etc. However, conventional positioning sensors, such as PIR, ultrasonic, microwave etc. are vulnerable to weather or insensitive to direction of subject movement or low precision performance. In this paper we implement a UWB-IR localization system for long distance and high-precision localization, which is not affected by temperature, light and weather. The proposed system was divided and designed by H/W, Antenna, S/W parts, each of which was designed based on an accurate analysis and simulation. As a result, we can implemented and verified UWB IR system with precise localization performance.

• Korean Journal of Remote Sensing
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• v.3 no.2
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• pp.89-102
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• 1987

Microwave remote sensing plays a major role in areas where cloud cover and darkness prevail. In this and the next paper, models are described for the radar backscatter from two major types of sea ice in an attempt to specify optimum sensor parameters and to allow the most reliable image interpretation possible. Here, the physical-optics model using an exponential correlation function is shown to be able to presict the signatures of first-year ice under cold conditions. The effect of volume scattering by small inclusions in the first-year ics is shown to be negligible using a semi-empirical volume scattering model.

• Electronics and Telecommunications Trends
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• v.34 no.5
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• pp.26-35
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• 2019

Modern imaging technologies utilizing electromagnetic waves are indispensable in our daily lives. Applications, such as television and smartphone screens, radar imaging for weather forecast, and medical imaging, can be attributed to technology developments in various electromagnetic regions. Terahertz (THz) waves, electromagnetic (EM) waves located between far infrared and microwave regions, had left unexplored EM waves. Recent advances in technology have led to various two-dimensional and three-dimensional THz imaging techniques. In this article, we explain THz imaging techniques as well as the experimental results from our laboratory. Additionally, we introduce commercial THz cameras developed worldwide. Finally, we present the applications of THz imaging techniques.

• International journal of advanced smart convergence
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• v.11 no.2
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• pp.53-58
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• 2022

In this paper, w-band frequency synthesizer was developed for frequency-modulated continuous wave (FMCW) radar sensors. To achieve a small size and high performance, We designed and manufactured w-band MMIC chips such as up-converter one-chip, multiplier, DA (Drive Amplifier) MMIC(Monolithic Microwave Integrated Circuit), etc. And interposer technology was applied between the W-band multiplier and the DA MMIC chip. As a result, the measured phase noise was -106.10 dBc@1MHz offset, and the frequency switching time of the frequency synthesizer was less than 0.1 usec. Compared with the w-band frequency synthesizer using purchased chips, the developed frequency synthesizer showed better performance.

• Korean Journal of Remote Sensing
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• v.38 no.4
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• pp.375-386
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• 2022

The city of Khartoum, the capital of Sudan, was heavily damaged by the flood of the Nile in 2020. Classification using satellite images can define the damaged area and help emergency response. As Synthetic Aperture Radar (SAR) uses microwave that can penetrate cloud, it is suitable to use in the flood study. In this study, Random Forest classifier, one of the supervised classification algorithms, was applied to the flood event in Khartoum with various sizes of the training dataset and number of images using Sentinel-1 SAR. To create a training dataset, we used unsupervised classification and visual inspection. Firstly, Random Forest was performed by reducing the size of each class of the training dataset, but no notable difference was found. Next, we performed Random Forest with various number of images. Accuracy became better as the number of images in creased, but converged to a maximum value when the dataset covers the duration from flood to the completion of drainage.

• Korean Journal of Remote Sensing
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• v.27 no.2
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• pp.191-201
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• 2011

Soybean has widely grown for its edible bean which has numerous uses. Microwave remote sensing has a great potential over the conventional remote sensing with the visible and infrared spectra due to its all-weather day-and-night imaging capabilities. In this investigation, a ground-based polarimetric scatterometer operating at multiple frequencies was used to continuously monitor the crop conditions of a soybean field. Polarimetric backscatter data at L, C, and X-bands were acquired every 10 minutes on the microwave observations at various soybean stages. The polarimetric scatterometer consists of a vector network analyzer, a microwave switch, radio frequency cables, power unit and a personal computer. The polarimetric scatterometer components were installed inside an air-conditioned shelter to maintain constant temperature and humidity during the data acquisition period. The backscattering coefficients were calculated from the measured data at incidence angle $40^{\circ}$ and full polarization (HH, VV, HV, VH) by applying the radar equation. The soybean growth data such as leaf area index (LAI), plant height, fresh and dry weight, vegetation water content and pod weight were measured periodically throughout the growth season. We measured the temporal variations of backscattering coefficients of the soybean crop at L, C, and X-bands during a soybean growth period. In the three bands, VV-polarized backscattering coefficients were higher than HH-polarized backscattering coefficients until mid-June, and thereafter HH-polarized backscattering coefficients were higher than VV-, HV-polarized back scattering coefficients. However, the cross-over stage (HH > VV) was different for each frequency: DOY 200 for L-band and DOY 210 for both C and X-bands. The temporal trend of the backscattering coefficients for all bands agreed with the soybean growth data such as LAI, dry weight and plant height; i.e., increased until about DOY 271 and decreased afterward. We plotted the relationship between the backscattering coefficients with three bands and soybean growth parameters. The growth parameters were highly correlated with HH-polarization at L-band (over r=0.92).

• Korean Journal of Remote Sensing
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• v.34 no.6_4
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• pp.1503-1517
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• 2018

Mt. Baekdu is a stratovolcano located at the border between China and North Korea and is known to have formed through its differentiation stage after the Oligocene epoch in the Cenozoic era. There has been a growing interest in the magma re-activity of Mt. Baekdu volcano since 2010. Several research projects have been conducted by government such as Korea Meteorological Administration and Korea Institute of Geoscience and Mineral Resources. Because, however, the Mt. Baekdu volcano is located far from South Korea, it is quite difficult to collect in-situ observations by terrestrial equipment. Remote sensing is a science to analyze and interpret information without direct physical contact with a target object. Various types of platform such as automobile, unmanned aerial vehicle, aircraft and satellite can be used for carrying a payload. In the past several decades, numerous volcanic studies have been conducted by remotely sensed observations using wide spectrum of wavelength channels in electromagnetic waves. In particular, radar remote sensing has been widely used for volcano monitoring in that microwave channel can gather surface's information without less limitation like day and night or weather condition. Radar interferometric technique which utilized phase information of radar signal enables to estimate surface displacement such as volcano, earthquake, ground subsidence or glacial movement, etc. In 2018, long-term research project for collaborative observation for Mt. Baekdu volcano between Korea and China were selected by Korea government. A volcanic specialized research center has been established by the selected project. The purpose of this paper is to introduce about remote sensing techniques for volcano monitoring and to review selected studies with remote sensing techniques to monitor Mt. Baekdu volcano. The acquisition status of the archived observations of six synthetic aperture radar satellites which are in orbit now was investigated for application of radar interferometry to monitor Mt. Baekdu volcano. We will conduct a time-series analysis using collected synthetic aperture radar images.

• Journal of the Korean Society of Marine Environment & Safety
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• v.15 no.4
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• pp.283-288
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• 2009

Estimations of oil slick area after M/T Herbei Sprit accident in December 2007 were analyzed using ENVITSAT ASAR(Advanced Synthetic Aperture Radar) microwave and KOMPSAT-2 of high resolution data. Monthly end short-term variations of chlorophyll a concentration before end after M/T Herbei Sprit oil spill accident were also analyzed using SeaWiFS/MODIS ocean color data. The oil slick areas estimated by KOMPSAT-2 and ASAR satellites were 59,456 $m^2$ and 1,168 $km^2$, respectively. The winds before end after oil spill accident were prevailed the northerly and northwesterly winds, and the strength of wind in this accident was stronger than 10 m/sec. In Taean and Anmeon-do, monthly mean chlorophyll a concentrations(6.3 mg/$m^3$ and 3.7 mg/$m^3$) in January 2008 alter the oil spill were higher than those(2.9 mg/$m^3$ and 2.5 mg/$m^3$) in December 2007. Short-term variations of chlorophyll a in these areas were decreased alter one or two weeks of oil spill.