• The Journal of the Korea institute of electronic communication sciences
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• v.13 no.2
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• pp.321-326
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• 2018

This study describes the design and implementation of TRM(Transmit and Receiver Module) for detection for targets of small RCS(Radar Cross Section). Through the pre-simulation analysis of radar system about RF, the main specifications of TRM are verified. After the fabrication of TRM, the main characteristics such as the maximum output, noise figure, spurious were confirmed. In the future, the radar system test will be carried out by assembling TRMs, antenna radiator, and the transceiver that generates and receivers the radar waveform reflected.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.20 no.2
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• pp.13-17
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• 2012

The solar storm generated by solar activity can be impact on earth in various area. If solar storm impact on Navaids system, it will be a serious problem for aviation and human safety. The impact analysis of solar strom on Navaids system are performed in three area, ILS, GPS navigation and radio communication for aviation. Analysis result show that Instrument Landing System(LLZ, GP, MB) and Navaids system(VOR, DME, Radar) are not impacted by the solar storm, but GPS system is impacted by solar storm. Also analysis result show that VHF/UHF radio system are not impacted by solar storm, but HF radio system is impacted by solar storm.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2016.05a
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• pp.276-278
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• 2016

해상교통관제는 RADAR, AIS, CCTV 등 수많은 장비로부터 얻을 수 있는 정보들을 관찰, 판단, 해석하는 상황인식 과정을 거쳐 이를 바탕으로 선박 안전운항에 필요한 '정보제공, 조언 권고, 지시'를 무선통신기기(VHF무선전화)를 통해 전달하는 일련의 과정이다. 선박과의 최종적인 정보교환체계인 무선통신기술은 과학기술의 발전에 힘입어 꾸준히 발전되고 개선돼 오고 있지만, 여전히 많은 한계점들을 내재하고 있다. 이 글을 통해 VHF를 통한 해상교통관제의 한계점들에 대해 알아봄으로써 관제사들의 VHF에 대한 특성 및 한계점에 대한 이해를 돕고 이를 극복하기 위한 방안들을 제시하고자 한다.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2018.05a
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• pp.237-239
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• 2018

선박관제용 VTS시스템은 레이더, 선박자동식별장치(AIS) 등을 이용하여 정보를 수집하여 관제정보가 필요한 선박국에게 초단파무선통신(VHF)를 통하여 전달한다. 레이더와 선박자동식별장치(AIS) 등은 장비를 이중화하여 안정적인 운영을 할 수 있지만, 관제장비에서 가장 중요한 역할을 담당하는 초단파무선통신(VHF)는 장비만을 이중화하는 것으로 부족한 이유는 바로 주로 선박국이나 육상국에서 일어나고 있는 KEYING현상 때문이다. 최근 제주, 목포, 완도, 여수연안 VTS 등에서 동시 발생한 VHF KEYING 현상을 분석하여 효율적인 대응 방안을 제시하고자 한다.

• The Bulletin of The Korean Astronomical Society
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• v.36 no.2
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• pp.81.1-81.1
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• 2011

The new coherent scatter ionospheric radar has been operating at Gyerong city ($36.18^{\circ}N$, $127.14^{\circ}E$, dip lat $26.7^{\circ}N$), South Korea. This VHF radar is consisted of 24 Yagi antennas having 5 elements and observes the E- and F-region field-aligned irregularities (FAIs) in a single frequency of 40.8 MHz with a peak power of 24 kW. We present the first results of the E- and F-region FAIs over Korea by using the new VHF coherent scatter ionospheric radar. The morphological and echo characteristics are studied in terms of their echo strength, Doppler velocity and also by spectral width values. From the continuous observations from December 2009, we found ionospheric E- and F-region FAIs appeared frequently. The most interesting and striking observations for E region are occurrence of daytime E-region irregularities and strong Quasi-Periodic (QP) echoes at nighttime. And for F region, strong post-sunset and pre-sunrise FAIs appeared frequently. The VHF radar observations over Korea are discussed in the light of current understanding of mid-latitude E- and F-region FAIs.

• Journal of Navigation and Port Research
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• v.45 no.4
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• pp.204-211
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• 2021

The Maritime Domain Awareness system is a component that is necessary to enhance the awareness of all situations occurring at sea in relation to security, safety, economy, and the environment. To establish a marine situation recognition system that is currently being introduced in major maritime countries after approval by the International Maritime Organization's Maritime Safety Committee in 2010, operational measures should be established. For the purpose of establishing a technological foundation for the efficient construction of a Korean maritime situation recognition system, this study analyzed the status of each system (RADAR, VHF, and V-PASS, etc.) and proposed the application of data and communication standards.

• Journal of the Korea Institute of Military Science and Technology
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• v.11 no.6
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• pp.55-62
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• 2008

An Estimation of VHF datalink range for EW(Electronic Warfare) equipment in the sea environment was studied to predict the datalink range between transmitting and receiving station. We consider refraction and reflection in addition to the basic radar equation. The reflection especially includes propagation factor in case of spherical earth as well as flat earth. The estimation result can predict the real datalink range within 5% error.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.29 no.6
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• pp.473-476
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• 2018

Herein, a $2{\times}2$ subarray antenna is designed to implement a VHF band active electronically scanned array. The Yagi-Uda antenna is used as a radiating element. The bandwidth enhancement and miniaturization of the Yagi-Uda antenna are achieved by optimizing the diameter of a driven element and the length of a director. In addition, the grid reflector is utilized to improve the front-to-back ratio(FBR) and to reduce both the wind resistance and overall system weight. The fabricated $2{\times}2$ subarray antenna fully covers the VHF target band($0.98{\sim}1.02f_c$). The measured maximum gain is 10.61 dBi and the FBR is larger than 26 dB.

• The Bulletin of The Korean Astronomical Society
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• v.37 no.2
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• pp.127.1-127.1
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• 2012

The 40.8-MHz VHF coherent scatter ionospheric radar, located in South Korea (Gyeryong, $36.18^{\circ}N$, $127.14^{\circ}E$), has been operating since December 2009 to investigate ionosphere E- and F-region field-aligned irregularities (FAIs) of mid-latitude. During the observation, we found E- and F-region FAIs appeared frequently: continuous echoes during the post-sunrise period and Quasi-Periodic (QP) echoes at nighttime for E region ; strong post-sunset and pre-sunrise FAIs for F region. The characteristics of E- and F-region FAIs are presented in terms of seasonal and local time variations of occurrence during December 2009 to August 2012. In addition, to investigate the correlation with geomagnetic activity to FAIs occurrence, we compared K-index variations to local time occurrence. It is worth to note our occurrence result since long term observation over several years in the mid-latitude has not yet been carried out.

• Journal of Astronomy and Space Sciences
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• v.31 no.1
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• pp.15-23
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• 2014

We present preliminary observations of the field-aligned-irregularities (FAIs) in the E and F regions during the solar minimum (2009 - 2010) using the 40.8 MHz coherent backscatter radar at Daejeon ($36.18^{\circ}N$, $127.14^{\circ}E$, $26.7^{\circ}N$ dip latitude) in South Korea. The radar, which consists of 24 Yagi antennas, observes the FAIs using a single beam with a peak power of 24 kW. The radar has been continuously operated since December 2009. Depending on the manner of occurrence of the backscatter echoes, the E-region echoes are largely divided into two types: quasi-periodic (QP) and continuous echoes. Our observations show that the QP echoes occur frequently above an altitude of 105 km in the post-sunset period and continuous echoes occur preferentially around an altitude of 105 km in the post-sunrise period. QP echoes appear as striated discrete echoes for a period of about 10 - 20 min. The QP-type echoes occur more frequently than the continuous-type echoes do and the echo intensity of the QP type is stronger than that of the continuous type. In the F region, the FAIs occur at night at an altitude interval of 250 - 450 km. As time proceeds, the occurrence height of the FAIs gradually increases until early in the morning and then decreases. The duration of the F-region FAIs is typically a few hours at night, although, in rare cases, FAIs persist throughout the night or appear even after sunrise. We discuss the similarities and differences of the FAIs observed by the Daejeon radar in comparison with other radar observations.