• Nuclear Engineering and Technology
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• v.56 no.1
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• pp.216-221
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• 2024

Ion cyclotron range of frequency (ICRF) heating system is an important auxiliary heating method in the experimental Advanced Superconducting Tokamak (EAST). In EAST, several megawatts of power are transmitted with coaxial transmission lines and coupled to the plasma. For the long pulse and high power operation of the ICRF waves heating system, it is very important to effectively control the power and initial phase of the ICRF signals. In this paper, a power and phase feedback control system is described based on field programmable gate array (FPGA) devices, which can realize complicated algorithms with the advantages of fast running and high reliability. The transmitted power and antenna phase are measured by a power and phase detector and digitized. The power and phase feedback control algorithms is designed to achieve the target power and antenna phase. The power feedback control system was tested on a dummy load and during plasma experiments. Test results confirm that the feedback control system can precisely control ICRF power and antenna phase and is robust during plasma variations.

• Journal of the Korea Institute of Military Science and Technology
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• v.18 no.3
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• pp.275-282
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• 2015

Recently, telemetry systems are used to test and evaluate of ammunition. When a transmitting signal from a small transmitter mounted inside the ammunition is sent out, the receiving equipments get real-time RF data. This paper relates to the development of a small high-G endurable transmitter and a portable receiving equipment. The system was tested and confirmed 00 km communication range.

• Journal of the Korea Institute of Military Science and Technology
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• v.7 no.3 s.18
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• pp.93-100
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• 2004

In this paper, we describe the design, fabrication, and test results of a W-band FMCW radar for the metal target detection under the ground clutter environment. In order to detect metal targets on the ground, we used a single cassegrain antenna with the beamwidth of $1.45^{\circ}$ which forms pencil-beam footprint on the ground. A log envelope detector was applied to improve radar performance in the severe ground clutter known as Weibull and log normal clutter. The designed FMCW radar can acquire altitude information from the ground clutter with $\sigma_0=-23dB$ at the height of 160m. The fabricated W-band FMCW radar transmits 11 dBm power and the dynamic range of the receiver is from -106dBm to -30dBm. The performances of the fabricated sensors were tested out in the fields and detected a car target of 200m apart on the grass.

• Proceedings of the Korean Society of Marine Engineers Conference
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• 2005.06a
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• pp.1005-1010
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• 2005

In this paper, it is presented a frequency modulated continuous wave radar (FMCW) for distance measurement. The frequency range is $10{\sim}11$ GHz and the sweep time of the signal is 100 ms. The test target is 0.8 m2 of metal plate. The experiment is performed in open ground and the pyramidal horn antenna of about 22 dBi gain is used. The beat frequency according to the target moving to 40 m is measured. There is a good agreement between measured and calculated results. But the resolution of the FMCW radar is not good such as about 10 cm. It is result from the nonlinear signal of voltage controlled oscillator (VCO). To improve the nonlinear characteristic of VCO, a high pass filter and phase locked loop (PLL) frequency synthesizer are included in the radar system.

• Korean Journal of Remote Sensing
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• v.10 no.2
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• pp.1-15
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• 1994

Since Seasat SAR mission in 1978, SAR has become one of the most important surface imaging tools in satellite remote sensing SAR achieves high resolution by signal processing synthesizing a larger aperture. Therefore, SAR signal processing along with antenna technology has been centered upon SAR technologies. Thus interpreters of SAR imagery as well as those who involved in signal processing require the knowledge of the principal SAR processing algorithm. Although the conventional range-Doppler approach has been widely adopted by many SAR processors, azimuth compression including the range migration has been problematic. The recent development of the wavenumber domain approace is able to provide high precision SAR focusing algorithm. Compared with the wavenumber domain algorithm derived by applying Born (first) approximation, the transfer function of the conventional range-Doppler algorithm accounts only for the first order approximation of the exact transfer function. The results of a simulation and an actual test using airborne C-band SAR configuration demonstrate the dxcellent performance of the wavenumber domain algorithm.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.22 no.3
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• pp.336-344
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• 2011

The purpose of this study is to analyze the radiation-pattern characteristics above 1 GHz for the electromagnetic wave radiated from multi-slot such as ventilations, etc. on the enclosure of an EUT and so to make recommendations for suitable test methods. An experimental EUT was formed by putting a comb-generator at the center of a rectangular enclosure with 4 slots, and its radiation pattern was analyzed in the frequency range of 1~6 GHz. As analysis results, multi-lobe appears above 2 GHz and the number of multi-lobes is growing as the frequency increases. And real radiated-emission measurements were performed for the experimental EUT by scanning a receiving antenna in the height of 1~4 m and tilting toward maximum radiation, as well as setting the height of a receiving antenna to the central position of the EUT which is prescribed at the present standards. The measured results are +12.8 dB in the scanning and +16.4 in the scanning and tilting compared with the present standard test method. Therefore, the latter must be revised in order to consider the radiation pattern above 1 GHz.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.21 no.4
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• pp.371-380
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• 2010

The CATR(Compact Antenna Test Range) is a testing facility which is to provide the uniform plane wave by using the reflector. As the ripple of the uniform plane wave caused by the diffraction rays at the edge of the reflector, serrations are attached at the edge of the reflector to minimize the ripple of the uniform plane wave in the CATR. The diffraction field of the serration is normally analyzed by the Fresnel diffraction formula which is expressed as the double integration, and the structure of the serration is expressed as Fourier series to apply the double integration of the Fresnel diffraction formula. In this paper, the novel shark-fin shaped serrations which have the height modulation of the adjacent serrations are proposed. And the triangular serrations and the novel shark-fin shaped serrations are compared to confirm that the performance of the quiet zone by the shark-fin shaped serrations is better than by the triangular serrations. It is also confirmed that the novel shark-fin shaped serrations which have the height modulation of the adjacent serrations are lower ripple than which have the same height of the adjacent serrations. Accordingly, the novel shark-fin shaped serrations with the height modulation can be used at the edge of the reflector to provide the uniform plane wave in CATR.

• Korean Journal of Ecology and Environment
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• v.47 no.3
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• pp.225-231
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• 2014

Discharge measurement during flood season is very difficult. Microwave water surface current meter (MWSCM) can measures river surface velocities easily without contacting water. This study introduces its improved version, MWSCM for general use. The existing version of MWSCM is for floods so that its applicable period in a year is short. It has been improved to extend its applicability in a year. The range of measurable velocity for MWSCM for general use is extended so it can be applied during normal flows as well as high flows. MWSCM for general use can measure the velocity range of $0.03{\sim}20.0ms^{-1}$, whereas MWSCM for floods can measure the velocity range of $0.5{\sim}10.0ms^{-1}$. To make such innovation of MWSCM for general use, the applied microwave frequency of MWSCM was changed from 10 GHz to 24 GHz. Waveguide slot array antenna has been designed with the new development of the circuit of transmitting and receiving part. Improvement requests on the existing MWSCM for floods - weight lightening, measured velocity stabilization, self-test, low power consumption, and waterproof and dampproof - from the users of it have been reflected for the development of the new version of MWSCM.

• Journal of Navigation and Port Research
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• v.28 no.6
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• pp.497-501
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• 2004

In this paper, it is presented a level sensor for measuring a level of the contents of cargo tank using frequency modulated continuous wave(FMCW). The frequency range is 10∼11 GHz, the radar cross section(RCS) of test target is $0.8\textrm{m}^2$ of metal plate. The experiment is performed in laboratory and open ground, the sweep time of the signal is 100 ms, the pyramidal horn antenna of about 22 dBi gain is used, and input power of antenna is about 8 dBm The beat frequency according to the target moving to 40 m is measured. There is a good agreement between measured and calculated results. But the resolution of the FMCW radar is measured about 10 cm due to nonlinear of voltage controlled oscillator(VCO).

• Journal of the Korea Institute of Information and Communication Engineering
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• v.23 no.4
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• pp.445-452
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• 2019

Today, most detection systems used in the marine industry are the majority of devices operating in the high-power X-band bands. While most detection systems using these frequencies in the X-Band band can expect a wide range of detection performance, they are not suitable for precision detection and have the limitation that they are large and heavy. In this paper, we designed, fabricated and tested an electronic scanner capable of detecting not only the surrounding objects but also the ocean waves at a low power of less than 2W in the 17GHz frequency band of the Ku-Band. A high-performance patch array antenna and Doppler effect were utilized to obtain sufficient detection performance even at low power. As a result of the test, it was confirmed that the performance was sufficiently valuable.