• Journal of Korea Water Resources Association
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• v.53 no.1
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• pp.15-27
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• 2020

Streamflow discharge as a fundamental riverine quantity plays a crucial role in water resources management, thereby requiring accurate in-situ measurement. Recent advances in instrumentations for the streamflow discharge measurement has complemented or substituted classical devices and methods. Among various potential methods, surface current meter using microwave has increasingly begun to be applied not only for flood but also normal flow discharge measurement, remotely and safely enabling practitioners to measure flow velocity postulating indirect contact. With minimized field preparedness, this method facilitated and eased flood discharge measurement in the difficult in-situ conditions such as extreme flood in active ways emitting 24.125 GHz microwave without relying on natural lights. In South Korea, a rectangular shaped instrument named with Microwave Water Surface Current Meter (MWSCM) has been developed and commercially released around 2010, in which domestic agencies charging on streamflow observation shed lights on this approach regarding it as a potential substitute. Considering this brand-new device highlighted for efficient flow measurement, however, there has been few noticeable efforts in systematic and comprehensive evaluation of its performance in various measurement and riverine conditions that lead to lack in imminent and widely spreading usages in practices. This study attempted to evaluate the MWSCM in terms of instrumen's monitoring configuration particularly regarding tilt and yaw angle. In the middle of pointing the measurement spot in a given cross-section, the observation campaign inevitably poses accuracy issues related with different tilt and yaw angles of the instrument, which can be a conventionally major source of errors for this type of instrument. Focusing on the perspective of instrument configuration, the instrument was tested in a controlled outdoor river channel located in KICT River Experiment Center with a fixed flow condition of around 1 m/s flow speed with steady flow supply, 6 m of channel width, and less than 1 m of shallow flow depth, where the detailed velocity measurements with SonTek micro-ADV was used for validation. As results, less than 15 degree in tilting angle generated much higher deviation, and higher yawing angle proportionally increased coefficient of variance. Yaw angles affected accuracy in terms of measurement area.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.21 no.10
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• pp.1073-1084
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• 2010

In this paper, the bio-heat equation including thermoregulatory functions is solved for an anatomically based human head model comprised of 14 tissues to study the thermal implications of high-power exposure to electromagnetic(EM) fields due to half-wave dipole antenna both at 835 and 1,800 MHz. The dipole antenna is located at the side of the ear and the front of the eyes. The FDTD method has been used for the SAR computation. When solving the BHE, the thermoregulation function and sweating effetecs are included in order to predict more exact temperature increase. It is noted that an approximately proportional relationship between the tissues and the maximum temperature increase and the antenna power is not maintained when the thermoregulation and sweating effects are fully accounted for under high power exposure.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.49 no.1
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• pp.73-77
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• 2012

In this article, we designed a wide bandpass filter in order to apply microwave reflectometry for KSTAR. The proposed wide bandpass filter consists of a metamaterial structure which is to get a wide band, a lower insertion loss, and a high skirt. This is applied to VCO's output to enhance the linearity. A pass band is 18-28 GHz and the out of pass band is stopped over 20 dB. To confirm of the metamaterial, we suggest a dispersion diagram. The proposed filter in lower band and upper band of pass band is respectively a left handed and right handed characteristics. A group delay is below 0.5 ns.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.28 no.7
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• pp.519-527
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• 2017

The trust issue on the safety of autonomous vehicle is a very important in regard to the demand generation of relevant industries. To secure the trust, The study of legal liability issue should be prior to an accident of the autonomous vehicle. In civil law, it is possible to make the automobile manufacturer take legal responsibility with the "Product Liability Act". Whereas, in criminal law, it is difficult to make him take legal responsibility since the criminal law holds the actor responsible. To solve these problems, this article proposes the establishment of the "Special Act on Autonomous Vehicle". Also, there is a demand for building infra structures and system to operate the (fully) self-propelled vehicle and establishing "certification" systems.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.21 no.4
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• pp.340-351
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• 2010

This paper presented compact CW sub-THz imaging system using the terahertz transmitter(Tx) that generates 0.34 THz electromagnetic wave based on electronic device. Using 0.34 THz electromagnetic wave generated by Tx, we measured transmitting terahertz wave magnitude and phase information respectively with terahertz receiver(Rx) based on sub harmonic mixer. This paper measured and compared images of several samples to obtain better imaging results by changing time delay and step distance of scanning stage which affect image resolution. Also, through the imaging measurement of various samples, we were able to assure possibility of application of terahertz wave.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.24 no.10
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• pp.1001-1007
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• 2013

In the case of multi-mission LEO(Low Earth Orbit) operations, depending on the orbit of each satellite, one ground site is supposed to be communicated with more than two satellites at the same time. On top of that, image data processing system is generally mission-specific and 1:1 backup configuration. For the reason, if ground site has smaller number of antenna than that of satellite, interface with image data processing system would be very complicated. In this paper, considering that two LEO satellites can be operating and image data recording unit in redundancy can be easily plug-in, the implementation of matrix receiving structure is described. This matrix receiving structure has been validated from KOMPSAT-2 and -3(KOrea Multi-Purpose SATellite-2 and -3) since KOMPSAT-3 was launched in May, 2012. This structure will be applied for the KOMPSAT-3A and -5 through its expandability.

• Proceedings of the KIEE Conference
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• 2002.11d
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• pp.347-349
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• 2002

350km/h의 주행속도를 목표로 개발, 시험중인 한국형 고속전철의 안전한 주행과 발생 전자파의 영향 저감을 통한 주변장치의 영향 최소화를 위하여 저속 운행부터 입력전류를 측정한다. 이때 LabVIEW Program을 이응하며. 계측되고 분석된 결과를 토대로 차량의 설계 대비 성능의 확인 및 향후 고속주행을 위한 기본 자료로 활용하고자 한다.

• The Proceeding of the Korean Institute of Electromagnetic Engineering and Science
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• v.10 no.3
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• pp.48-57
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• 1999

안테나 단에서 직접 수신 신호의 디지털화가 이루어지고 그 해당 신호의 처리는 고속 디지털 신호처리기 내에서 소프트웨어로 수행되는 방식을 SWR(Software Radio)이라 한다. 그러나 현재의 기술 수준을 감안하여 보다 현실적인 SDR(Software Defined Radio) 정의가 필요하게 되었다. SDR이란 수신신호의 디지털화가 안테나 이하의 임의의 단(IF단)에서 이루어지는 무선으로 정의된다. 물론 A/D변환기등의 기술이 더욱 발전되면 궁극적으로는 SWR로 진화될 것이다. 그러면 SDR은 왜 필요한 것일까? 현재 사용중인 이동통신 단말기의 단점은 어느 한 표준 또는 방식에 종속되어 언제 어디서나 임의의 시스템에 접속되어 사용하기에는 많은 기술 종속적인 문제 및 제약을 내포하며, 사용방식에 따른 시스템의 유연성이 없고, 상용 서비스 도중에 발생되는 단말기 문제의 해결(recall service)이 어렵고, 많은 기술료를 지불해야 한다는 것이다. 부연하면 CDMA 셀룰라의 경우 퀄컴 등의 특정한 회사에 의해 기술이 폐쇠되어, 정보의 흐름이 자유스럽지 못할 뿐더러, 이로 인해 기술진화가 보다 빠르게 진행되지 못하고, 전세계적으로 많은 새로운 우수 제품의 출연에 제약이 가해진다는 것이다. 따라서 SDR(Software Defined Radion)을 도입, 하드웨어 및 소프트웨어를 개방형 구조(open architecture)로 개발한다면 정보의 흐름을 자유롭게 할 수 있고, 이로 인하여 세계적으로 다양한 신제품의 개발이 촉진되고 결과적으로 전세계 시장이 커지게 되는 일석이조의 효과를 얻을 수 있게 된다. 또한 이 같은 개방형 단말기 개발의 필요성은 최근 시장동향으로 볼 때, 기존의 단말기 회사 입장에서는 새로운 수익 모델이 필요한 시점이고, 또한 2002년경에 판매되는 단말기의 80%정도는 멀티모드타입 단말기일 것으로 예측되는 점, 그리고 금년말까지 100개 회사 이상이 SDR 포럼 멤버로 가입할 것으로 예측되는 점, 무선 인터넷 폭발적인 성장으로 복합 멀티미디어 단말기 시대가 다가오는 점 등으로 미루어 볼 때, 고객의 서비스 가치선택에 역점을 둔 기술을 중시해야 한다는 점에서 더욱 설득력을 지닌다. 따라서 이 같은 목적과 3세대 이동통신 및 인터넷 사용자의 증가, 반도체기술의 발전에 힘입어, 과거 군용 시스템에서 이용되던 SWR 기술을 상용시스템 특히 3세대 이동통신에 적용하려는 연구가 활발히 진행되고 있다. '96년 SDR 포럼이 결성되었는데, 목적은 휴대형 장치(hand-held devices), 기지국(base stations), 차량형 장치(mobile stations)를 포함하는 다중모드(multi-mode), 다중대역(multi-band) SDR을 위한 개방형 구조의 표준을 정하기 위함이다. 이 같이 public forum에 의한 표준(open architecture standard)이 정해지면 그 다음은 이를 어떻게 구현할 것인가가 문제가 될 것이다. 본고에서는 먼저 SDR 단말기 요구사항을 살펴보고, 이 요구사항들을 만족하는 SDR 단말기 구조, SDR 계층참조 모델, 그리고 기존의 단말기 구조와 SDR 계층참조 모델의 연관관계에 대해 살펴보고, 크게 두가지 종류의 단말기 즉 사용 SDR 단말기와 군용 SDR 단말기에 대해 살펴보고, 설계 절차 및 현재 시점에서 단말기 구현을 위해 해결해야 하는 기술적 과제를 살펴보고 결론을 언급한다.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.22 no.11
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• pp.1070-1077
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• 2011

This paper introduces a radar signal processing technique for intelligent rear view monitoring of an automobile. The linear frequency modulation-frequency shift keying(LFM-FSK) waveform, which is the combination of frequency modulation continuous wave(FMCW) and frequency shift keying(FSK) waveform, is employed to simultaneously estimate the range, relative aspect angle, and velocity of an automobile. Hence, it can be applied to monitor the rear view of an automobile. FMCW waveform has high range resolution capability, but it produces ghost targets under a multiple target environment. In contrast, FSK waveform can provide high velocity resolution and avoids the problem of ghost targets. However, it fails to identify multiple targets along the radar's line of sight. With LFM-FSK waveform, we can estimate the ranges and velocities of multiple targets with very high resolution, which avoids the ghost target problem of an FMCW waveform. Simulation result shows that LFM-FSK wavefrom is suitable for use in the lane change assistance system for an automobile.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.21 no.7
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• pp.761-768
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• 2010

This paper presents an effective method to achieve the wideband waveform for high resolution SAR(Synthetic Aperture Radar) using the frequency multiplication technique. And also this paper analyzes the root causes for the spectral regrowth due to 3rd-order intermodulation in chirp bandwidth expansion scheme using quadrature modulator and frequency multipliers. The amplitude and phase imbalance requirement are defined based on the simulation results in terms of quadrature channel imbalance. This minimizes the degradation of range resolution, peak sidelobe ratio and integrated sidelobe ratio. The wideband chirp generator using the frequency multiplier and memory map scheme was manufactured and the compensation technique was presented to reduce the spectral regrowth of SAR waveform by minimizing the amplitude and phase imbalance. After I and Q channel imbalance adjustment, the carrier level reduces －28.7 dBm to －53.4 dBm. Chirp signal with 150 MHz bandwidth at S-band expands to 600 MHz bandwidth at X-band. The sidelobe levels are reduced by about 8 to 9 dB by compensating the amplitude balance between I and Q channels.