• Journal of Advanced Marine Engineering and Technology
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• v.31 no.8
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• pp.970-974
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• 2007

A mixer is a key component in the wireless communication systems. In this paper, we design a mixer which is used in a frequency modulated continuous wave(FMCW) radar system. The frequency sweep range of the radar is from 10 GHz to 11 GHz. The transmitted and received signals of the FMCW radar are applied to LO and RF ports of the mixer, respectively, but the frequency difference between the two signals, which is called "a beat frequency" is under a few KHz and depending on the distance to target. Thus the isolation between the LO and RF ports is very important factor to design this mixer. In this paper we propose a single balanced resistive mixer using GaAs MESFET for this application. We first design a single-ended type resistive mixer using a simulation tool, then design a balanced type to increase the LO-to-RF isolation of the mixer. We fabricated the mixer on the substrate of dielectric constant 10 and thickness 0.635 mm. The measured results show that the isolation and conversion loss of the mixer over the frequency band is 20dB and 10.5dB, respectively. The LO input power for operating the proposed mixer is +3dBm, which is lower than a general conventional mixer's LO power. The 1 dB compression point is 6dBm.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2019.05a
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• pp.119-120
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• 2019

In order to verify the accuracy of wave measurement of the wave instrumentation system using X-band navigation radar, The validity of the results was obtained by analyzing the significant wave height around Ulleungdo. Especially, The correlations between the radar, wave height buoy and marine buoy for wave measurements were analyzed in season.

• Proceedings of the Korea Water Resources Association Conference
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• 2016.05a
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• pp.233-233
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• 2016

현재 한국건설기술연구원에서 X-밴드 이중편파레이더를 운영하고 있으며, 이 결과 NetCDF 파일형식의 레이더 관측자료가 생성되고 있다. 레이더 자료포맷인 Netcdf 자료의 경우 레이더 관측과정에서 발생한 결과를 극좌표 형식으로 저장하고 있어 이를 분석이나 시스템에 적용하여 활용하기 위해서는 격자좌표로 변환하는 것이 필요하고, 또한 다양한 자료 변환 및 추출작업을 텍스트 기반으로 하기 위해 다양한 사전 작업이 필요하여 일반사용자가 사용하는데 어려운 상황이다. 그래서 이를 쉽게 수행할 수 있도록 JAVA를 이용하여 윈도우 기반으로 사용할 수 있는 프로그램(KICTRadar4WIN) 프로그램을 개발하였다. KICTRadar4WIN 프로그램의 경우 레이더 자료 품질관리, 레이더 자료 관리, 레이더 자료 추출, 레이더 자료 표출의 4가지 기능을 포함하고 있다. ${\bullet}$ 레이더 자료 품질관리 - 원시자료에 QC 기준을 입력하여 QC된 레이더자료를 생성 ${\bullet}$ 레이더 자료관리 - CAPPI 자료생성 : 관측된 PPI 및 RHI 자료를 이용하여, CAPPI 자료를 생성 - QPE 자료생성 : CAPPI 자료를 이용하여 QPE 자료를 생 - QPE 자료보정 : 지점우량을 이용한 G/R비를 산정하여 QPE 보정자료를 생성 ${\bullet}$ 레이더 자료 추출 - 격자자료 추출 : PPI, CAPPI, QPE 자료를 TEXT 자료로 변환하여 저장 - 지점자료 추출 : 입력된 지점좌표 중심으로 선택한 범위의 평균값을 TEXT 파일로 저장 - 면적자료 추출 : 입력된 면적자료의 평균값을 추출하여 TEXT파일로 저장 ${\bullet}$ 레이더 자료 표출 - 영상표출 : PPI, CAPPI, QPE 관측변수 자료를 그림파일 생성 - KMZ 자료생성 : PPI, CAPPI, QPE 자료를 KMZ 파일 생성

• Journal of Advanced Marine Engineering and Technology
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• v.33 no.5
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• pp.756-761
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• 2009

In this paper, a X band voltage controlled oscillator is proposed. The oscillator uses a transistor as an oscillating element and its oscillating frequencies are controlled by the tuning voltage of varactor diode. Using the circuit simulation tools, the matching circuits between the transistor and varactor diode, its input and output matching circuits, and a feedback circuits are designed. The measured results of the fabricated oscillator show that its oscillation frequencies are from 10.50GHz to 10.88GHz according to the turning voltages of 1V to 18V, its output power levels are about 4.3dBm, and its phase noise is around -43.5dBc/Hz at 100kHz offset frequency of 10.5GHz.

• Proceedings of the Korea Water Resources Association Conference
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• 2017.05a
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• pp.358-358
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• 2017

한국건설기술연구원에서 소형 X-밴드 이중편파레이더를 2013년부터 운영하고 있으며, 이를 효과적으로 활용하기 위한 다양한 툴을 개발하였다. 웹을 이용한 실시간 수재해경보시스템을 구축하였고, 이중 모바일로 활용할 수 있는 내용을 중심으로 모바일앱을 개발하였다. 매년 레이더 활용효과를 높이기 위해 다양한 연구를 수행하고 있으며, 수재해경보시스템 분야로 개선을 하고 있다. 기준 도심침수사례를 바탕으로 지속시간별로 홍수피해 강우량 분석을 통해 경보기준 호우량을 결정하였으며 행정구역을 기준으로 적용하여 수재해경보시스템을 보완하였다. 경보기준으로는 주의보 및 경보 2단계로 정하였으며, 기준 지속 시간은 도심배수구역 및 도심유역을 고려하여 10분 및 1시간을 대상으로 결정하였다. 추후 초단기 레이더강우 예측시스템을 추가하여 수재해경보시스템의 활용 효과를 높일 계획이다.

• Journal of the Korea Institute of Military Science and Technology
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• v.26 no.3
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• pp.246-251
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• 2023

RADAR(Radio Detection and Ranging) is an important system for surveillance and reconnaissance by detecting a reflected signal which obtains the range from the radar to the target, and the velocity of the target. The magnitude of the reflected signal varies due to the radar cross section of the target, characteristic of the transmission and reception antenna, distance between the radar and the target, and power and wavelength of the transmitted signal. Thus, the RCS is the important characteristic of the target to determine if the target can be observed by the RADAR system. It is based on the material and shape of the target. We have measured the reflection signal of a simple square-shaped (20 × 20 cm) target made of a new material, a gallium-based liquid metal alloy and compared that of well-known metals including copper, aluminum. The magnitude of reflected signal of the aluminum target was the largest and it was 2.4 times larger than that of the liquid metal target. We also investigated the effect of the shape by measuring reflectance of the F-22 3D model(~1/95 ratio) target covered with/without copper, aluminium, and liquid metal. The largest magnitude of the reflected signal measured from side-view with the copper-covered F-22 model was 2.6 times greater than that of liquid metal. The reflectance study of the liquid metal would be helpful for liquid metal-based frequency selective surface or metamaterials.

• Journal of Advanced Marine Engineering and Technology
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• v.30 no.3
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• pp.444-448
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• 2006

In this paper, a frequency synthesizer for X-band FMCW radars is proposed. Some X-band FMCW radars have been used as a level sensor for tanker ship and the resolution of the level sensor may be mainly depend on linearity of frequency sweep. For a linear frequency sweep. the proposed synthesizer employs a phase-locked loop using prescalars and a high speed digital PLL chip. The measured results show that the linear frequency sweep range is from 10 GHz to 11 GHz and the output power of the synthesizer is minium 7 dBm. and the phase noise is about -80 dBc/Hz at 100 KHz offset from 11 GHz.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.3 no.4
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• pp.849-858
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• 1999

There are several improved designs of passive radar reflector available, but their performance is ultimately limited by the cross-section area and this is governed by the size of the buoy and the acceptable windage. Therefore it is needed to investigate the low-cost, low power, a active device that can be improve the reliability of response. Active Radar Reflector(AAR) consists of a microwave amplifier with separate receive and transmit antennas. It is a device which automatically transmits a signal in response to an interrogating signal received. It was intended to improve the consistency of the radar return from the buoy and the small craft, particularly in poor sea conditions. And it directly improves safety of navigation at sea.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2015.10a
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• pp.27-29
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• 2015

Based on IALA guidelines, the fundamental requirements of radar system for vessel traffic services are analyzed in this paper. target separation, target position accuracy, target track accuracy of X-band radar and recommended test conditions are analyzed. Also, in order to check if it satisfies the requirement of target position accuracy from IALA guideline, the test is carried out through processing of radar raw image acquired at VTS center.

• Journal of the Korean Society of Marine Environment & Safety
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• v.21 no.5
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• pp.571-576
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• 2015

This paper presents a comparative study of wave height estimation method that was used for signal to noise ratio and shadowing ratio based on X-band marine radar. If the signal to noise ratio, and is widely used as a method for estimating an wave height, a new method is presented for shadowing ratio. In the case of radar images used in this study it is measuring the data from the coast of Ulsan Jujeon, compared with marine meteorological information from the Meteorological Agency measured a light beacon. We compared the measured data for about 34 days, the typhoon was measured, incluidng a period in the East Sea, and verify the results for various distribution of wave height. For estimate wave height using a shadowing ratio analysis, it does not require calibration and real-time advantages of this part, coming confirmed the possibility of the measurement, the cause detection error for radar image was caused due to determine.