• The Journal of Korean Institute of Communications and Information Sciences
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• v.19 no.7
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• pp.1296-1303
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• 1994

In this paper, a design of active inductors and their application in a frequency converter are proposed. In MMIC design, passive spiral inductor takes larger area than any other passive and active elements. A conventional spiral inductor generates undesired crosstalk, and its performance cannot have certainty and reproducibility. Meanwhile the active inductor eliminates these drawbacks, and operates for much wider bandwidth. Furthermore, its size is smaller and nearly independent of inductance. the performance of MMIC frequency converter with active inductors is directly compared with that of the frequency converters with spiral inductors. The size is 28.6% smaller with better performance in MMIC frequency converter.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.47 no.8
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• pp.99-107
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• 2010

In a single frequency network (SFN) for Advanced Television Systems Committee (ATSC) terrestrial digital television (DTV) system, the interferences induced by the multiple transmitters and/or repeaters using the same frequency are inevitable. Since the presence of interferences results in performance degradation of the SFN, it is crucial to manipulate the interferences by adjusting the transmit power and timing of each transmitter and repeater. In the ATSC terrestrial DTV system, in order to facilitate the interference manipulation process, a transmitter identification (TxID) signal which is uniquely embedded in the signal to be transmitted from each transmitter and repeater is recommended. Even though the injection level of the TxID signal is much lower than the DTV signal, the TxID signal injection infects the DTV signal. Hence, the effect of the TxID signal on the DTV signal must be investigated before deployment. In this paper, the effect of the TxID signal on the performance of legacy DTV receivers under additive white Gaussian noise and multipath channel environments is investigated not only with computer simulation but also with laboratory and field tests. The test results show that the average threshold of visibility degradation of the legacy DTV receivers due to the TxID signal injection is less than 0.2 dB at the TxID injection level of -30 dB.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2011.11a
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• pp.254-257
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• 2011

Two types of thrusters(Descent Control Thruster (DCT) for reducing landing speed and Attitude Control Thruster (ACT) for attitude control) are mounted on the propulsion system of Ground test model lunar lander. In this paper, plume impingement effect and ground effect between DCT Modules are analyzed using numerical method when the impact occurred close to the ground.

• Proceedings of the Korea Institute of Convergence Signal Processing
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• 2001.06a
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• pp.33-36
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• 2001

In MC-CDMA systems effects of delay spread of the channel are reduced with increased symbol duration by simultaneously transmitting data symbols on the parallel subcarriers. However, the increased symbol duration causes the system to be more vulnerable to time selective fading. In this paper, we investigate the effects of time selective fading characteristics of the mobile channel from the viewpoint of desired signal power to inter-carrier interference power ratio at the combiner output of the MC-CDMA receiver.

• The Journal of the Acoustical Society of Korea
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• v.32 no.2
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• pp.124-130
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• 2013

The performance of underwater acoustic communication system is sensitive to the ISI(Inter-Symbol Interference) due to delay spread develop of multipath signal propagation. The equalizer is used to combat the ISI. In this paper, the performances of underwater acoustic communication with turbo equalizer were evaluated by real data collected in Korean littoral sea. As a result, when one iterative decoding using turbo equalizer is applied, the performance was improved 1.5 dB than the case of the non-iterative equalizer at BER $10^{-4}$. In the case of two or three iterations the performance was enhanced about 3.5 dB, but the performance wasn't improved any more in the case of more than three times.

• Journal of the Korea Computer Industry Society
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• v.2 no.4
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• pp.537-546
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• 2001

Griffth's and LCCMA which are Single-user detection adaptive algorithm are proposed for mitigate MAI(multiple access interference) and the near-far problem in direct-sequence spread-spectrum CDMA system and MOE Algorithm is proposed for MMSE(Minimum Mean-Square Error). This paper pertains to three types of Blind adaptive algorithms which can upgrade system functionality without the requirements from training sequence. It goes further to compare and analyze the functionalities of the algorithms as per number of interfering users or data update rate of the users. The simulation results was that LCCMA algorithm was superior to other algorithms in both areas. Blind application enabled a more flexible network design by eliminating the necessity of training sequence.

• Journal of Aerospace System Engineering
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• v.16 no.6
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• pp.18-23
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• 2022

This paper examines the electromagnetic shielding structure of ultra-high frequency (UHF) RF modules used in aircraft. Advances in electrical and electronic technologies have increased the need for electronic equipment in aircraft. High-frequency wireless devices have become integrated circuits in the form of UHF integrated circuits to support a wide range of frequencies and miniaturisation. To ensure the functionality and performance of these integrated devices in aviation, shielding is necessary to prevent unexpected electromagnetic interference, which could be detrimental to aircraft safety. A shield structure was designed to protect the RF chipset from malfunctioning, and the shielding effectiveness was improved through the application of various geometric shapes.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.16 no.2 s.93
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• pp.182-188
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• 2005

This paper presents an efficient technique for interference suppression in IEEE 802.11b WLAN systems. A linearly constrained adaptive array processor which may improve reception performance of WLAN device by reducing co-channel interference signal and multipath effects effectively was proposed. A spatial smoothing method is used to prevent cancellation of a desired signal in a coherent environment and also integral nulling method is employed to improve the array performance in indoor environment. It was shown that the integral nulling approach performed best while the spatial smoothing method performed better than linearly constrained array processing. The performance of the WLAN system may be improved by the proposed methods which reduce co-channel, coherent, and WPAN interferences effectively.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2010.07a
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• pp.18-19
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• 2010

ATSC 방식의 지상파 디지털 TV 방송에서는 단일 주파수 망 구성 시 송신기들과 중계기들이 단일 주파수를 사용함에 따라 수신기에서 간섭 문제가 발생한다. 이를 해결하기 위하여 ATSC 권고에서는 각 송신기 및 중계기에 RF Watermark 방식의 식별 (TxID: Transmitter Identification) 신호를 할당하여 송신 및 중계 신호에 부가하여 전송하도록 권고하고 있다. 본 논문에서는 기존 DTV 신호에 부가되어 전송되는 RF Watermark 방식의 TxID 신호가 상용 DTV 수신기에 미치는 영향을 분산주파수망을 이용하여 실제 필드 테스트를 통해 살펴본다.

• Proceedings of the IEEK Conference
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• 1999.11a
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• pp.821-824
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• 1999

In this article, as a way of pursuing high spectral efficiency and flexible cell planning, co-channel dual-polarization techniques are suggested for B-WLL applications. It provides a double down stream capacity compared with conventional scheme and also makes some flexibility in cell planning. In order to implement co-channel B-WLL system, some frequency plans, interference cancellation methods, and system block diagrams are presented here.