• 제어로봇시스템학회:학술대회논문집
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• 1997.10a
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• pp.1334-1337
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• 1997

A spacecraft attitude control ground hardware simulator development is discussed in the paper. The simulator is called KT/KARI HILSSAT(Hardware-In-the Loop Simulator Single Axis Testbed), and the main structure consists of a single axis bearing and a satellite main body model on the bearing. The single axis tabel as ans experimental hardware simulator that evaluates performance and applicability of a satellite before evolving and/or confirming a mew or and old control logic used in the KOREASAT is developed. Attitude control of spaceraft by using reaction wheel is performed.

• Journal of the Korean Society of Propulsion Engineers
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• v.3 no.4
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• pp.12-22
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• 1999

Operation of an electromagnetic shaker system using a Class-D amplifier may cause unacceptable electromagnetic interference to another electronic system, requiring the user to take whatever steps are necessary to correct the interference. A differential amplifier in a Class-D amplifier is used to decrease the effect of a common-mode noise voltage in a shaker system. To prevent a ground loop, a transformer is inserted in another shaker system. These methods show reduction of the unwanted vibration which has occurred before. A transformer in a charge amplifier was used to prevent a ground loop in a shaker system using a Class-AB amplifier a few years ago, but it was susceptible of noise in a shaker system using a Class-D amplifier. Hence we corrected a ground loop between a charge amplifier and a vibration control/analysis system without a transformer. The usefulness of this approach is illustrated by the results of experiments.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.23 no.5
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• pp.551-558
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• 2012

This paper presents a dual band loop-type ground antenna using lumped-elements that control the impedance bandwidth and resonant frequency. The dual-band operation of the proposed antenna is realized by inserting an additional resonated loop feed structure into the reference ground antenna. As the proper value of the capacitor and the inductor are chosen, the impedance bandwidth of our antenna with voltage standing wave ratio(VSWR) equal to 3 is 85 MHz and 725 MHz at the 2.45 and 5.5 GHz frequency band, respectively. Its validity is demonstrated via both the computed and measured results. Good antenna patterns and efficiencies are achieved at the dual frequency bands, as well as the physically small antenna element size($10{\times}5mm^2$).

• ETRI Journal
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• v.33 no.1
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• pp.121-124
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• 2011

Digital harmonics, which may reduce the radio frequency sensitivity of a system, can be coupled with an antenna in a mobile handset. This letter presents a decoupling method for increasing the isolation between digital harmonics on a flexible printed circuit board (FPCB) and an antenna in terms of the ground mode current and the concept of reaction. We model the signal and ground lines in an FPCB as a loop circuit exciting a ground mode current and demonstrate a simple but efficient decoupling method for reducing the excited ground mode current.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.14 no.3
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• pp.233-238
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• 2003

With the growth of high speed circuit, unwanted system noise is increased and multipoint ground is used to reduce this noise. PCB screw ground structure has radiation noise by ground loop between screws. In order to solve this problem, in this paper, we proposed improved PCB ground structure. Proposed structure improves noise absorption by using microwave absorber and conductive copper tape. We measured radiation PCB noise in the range of 1 ㎓ to 3 ㎓ to investigate proposed structure usefulness. From these results, under 2 ㎓ range proposed structure has noise reduction by 2.62 dBuV/m, which compared with screw ground.

• Journal of the Korean Solar Energy Society
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• v.33 no.1
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• pp.57-65
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• 2013

The temperatures with the ground depth, the positions of circulation water in ground heat exchanger were measured and thermal diffusion characteristics with the distances of the direction normal to the borehole was analysed. The deeper the depth of ground, the less the influences of outdoor temperature, but below 10m of ground, there was no influences of ground temperature. When the depth of trench pipe was below the depth of 2m, there was no influence. In the ground of 10m when the distances between the pipe and the other places were above 0.5m, the variations of temperature were less than $1.6^{\circ}C$ and above 2.5m they were less than $0.1^{\circ}C$. When the distances of bore hole were above 5m, there were no. influences of the nearest ground heat exchanger.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.28 no.1
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• pp.69-75
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• 2017

In this paper, slit ground resonator with slit and capacitor is proposed for practical use of magnetic resonant wireless power transfer(MR-WPT). And this paper presents the performance comparison of conventional loop resonator as Rx resonator to slit ground resonator. The proposed silt ground resonator with 31 cm width, 20.5 cm length, $35{\mu}m$ thickness is designed the crossing slit 1 cm width with only opened edge. And an external capacitors were connected at the opened edge of slit ground resonator for resonating at 6.78 MHz. The transfer efficiencies of MR-WPT were measured at open and short mode, and then the highest transfer efficiencies of MR-WPT according to the Rx resonators were plotted. In result, the transfer efficiency of MR-WPT with loop resonator was the highest. However, when the ground was inserted in receiver part at the bottom of laptop model, the transfer efficiency was closed 0 %. The transfer efficiency recovered the transfer efficiency of 67 % using slit ground resonator. The magnetic field was penetrated through the slit and proposed slit ground resonator works as resonator in MR-WPT.

• JSTS:Journal of Semiconductor Technology and Science
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• v.7 no.4
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• pp.241-246
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• 2007

This paper presents two novel compensation circuits for leakage current and power supply noise (PSN) in phase locked loop (PLL) using a nanometer CMOS technology. The leakage compensation circuit reduces the leakage current of the charge pump circuit and the PSN compensation circuit decreases the effect of power supply variation on the output frequency of VCO. The PLL design is based on a 32nm predictive CMOS technology and uses a 0.9 V power supply voltage. The simulation results show that the proposed PLL achieves 88% jitter reduction at 440 MHz output frequency compared to the PLL without leakage compensator and its output frequency drift is little to 20% power supply voltage variations. The PLL has an output frequency range of 40 $M{\sim}725$ MHz with a multiplication range of 1-1023, and the RMS and peak-to-peak jitter are 5psec and 42.7 psec, respectively.

• Proceedings of the Korea Electromagnetic Engineering Society Conference
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• 2003.11a
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• pp.278-282
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• 2003

The rapid growth of wireless and mobile communications has stimulated the development of multilayer filter technology. In this paper, one type of aperture-coupled microstrip interdigital-loop resonators in a multilayer structure are proposed and investigated for the applications to the design of a new class of compact microstrip bandpass filter. The new filter configuration consists of two arrays of microstrip interdigital-loop resonators that can be coupled through the apertures on the common ground plane. Depending on the arrangement of the apertures, different filtering characteristics can easily be realized. The results of measurement are almost similar to those of simulation.

• 한국방재학회:학술대회논문집
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• 2010.02a
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• pp.91.1-91.1
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• 2010

본 연구에서는 수직 밀폐형 지중 열교환기를 현장 시험시공하고 현장 열응답 시험을 수행하여 보어홀과 지반의 유효열전도도를 측정하였다. 뒤채움용 그라우트재는 벤토나이트와 시멘트가 고려되었으며 첨가제로는 천연규사와 흑연을 사용하고, 지중 열교환기 파이프 단면은 일반적으로 시공되는 U-loop 파이프 단면과 파이프 사이의 열간섭 효과를 최소화 한 3공형 파이프 단면이 착용되었다. 시멘트-천연규사 그라우트재가 벤토나이트-천연규사 그라우트재 보다 큰 유효열전도도를 보이고 흑연을 첨가한 그라우트는 시멘트와 벤토나이트 모두에서 천연규사만 첨가하였을 때 보다 유효열전도도가 높게 나타났다. 3공형 파이프 단면의 경우 단면에 따른 영향을 비교하기 위해 그라우트는 시멘트-천연규사와 벤토나이트-천연규사를 사용하였으며 유효 열전도도 측정결과 각각 3.65 W/mK, 3.40 W/mK으로 일반 U-loop 파이프 단면을 사용하였을 때 보다 높게 나타났다.