• 전기학회논문지
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• 제61권4호
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• pp.629-631
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• 2012

In Cognitive Radio network, spectrum selection scheme is one of a important part to manage idle spectrums efficiently. However, in CR networks, they have to adopt time-varying channel availability to minimize the interference to primary users (PU), and be able to manage spectrum resources efficiently. In this paper, we proposed a modified PF scheduler which can be appropriate to schedule downlink CR users and channels, by considering the fairness and the throughput as well as the primary user characteristics of each channel.

• 한국전자파학회:학술대회논문집
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• 한국전자파학회 2003년도 종합학술발표회 논문집 Vol.13 No.1
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• pp.183-187
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• 2003

The expression for the effects of an amplitude imbalance, a phase imbalance and a delay mismatch on the characteristics of a linearization loop in feedforward amplifiers is derived and analyzed. The simulation results are compared with the results obtained by means of using a commercial simulation tool and the exact agreement is reported.

• 한국광학회:학술대회논문집
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• 한국광학회 2006년도 하계학술발표회 논문집
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• pp.363-364
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• 2006

We developed 60 GHz analog optical transmitter modules for radio-over-fiber (RoF). They were consisted of an electroabsorption modulator (EAM), impedance matching circuit, and amplifier. The characteristics of fabricated modules were investigated by measuring the signal-to-noise ratio and the noise figure of the 60 GHz RoF link.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2007년도 추계학술대회 논문집
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• pp.1533-1540
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• 2007

The most critical function of the Communication Based Train Control system is wayside and on-board Radio communication. Radio communication must be safely made without errors. The standards for CBTC has not been established yet, and research on Radio communication systems for use in Train control systems adopting CBTC system such as the magnetic levitation train must continue. This paper will discuss the characteristics of Radio communication technology currently used domestically such as GSM-R, IEEE 802.11, TETRA, MESH, and WiMAX/WiBro, and will investigate the potential possibility of applying them to Train control systems.

• Journal of the Optical Society of Korea
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• 제14권4호
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• pp.351-356
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• 2010

We investigated the combined effect of fiber chromatic dispersion and self-phase modulation (SPM) in multi-channel subcarrier multiplexed (SCM) optical transmission systems. We theoretically analyzed the transmission characteristics of the SCM signals with the effect of SPM and chromatic dispersion in a single-mode optical fiber by numerical simulations based on the nonlinear Schrodinger equation. The numerical simulation results revealed that the effect of fiber dispersion and SPM could occur independently between subcarrier channels in two-channel SCM systems for small optical modulation index (OMI) and large channel spacing. However, for large OMI, small channel spacing, and large fiber launching power, we found a performance degradation of the two-channel system compared to that of a single-channel system. These parameters are therefore important for the optimization of multi-channel SCM systems applicable to radio over fiber networks.

• 한국산학기술학회논문지
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• 제6권5호
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• pp.401-406
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• 2005

디지털 신호 기억회로는 반도체 기술의 발달과 더불어 매우 빠른 속도로 발달되었다. 그러나 수 백 MHz 대역폭의 광대역 고주파 신호를 저장하였다가 복제하는 것은 매우 어려운 기술이다. 고주파 신호의 기억을 위해서 과거에는 아날로그 방식의 주파수 기억루프가 사용 되었으나, 광대역 신호 변환기와 광대역 주파수 증폭기 등이 개발 되면서 디지털 고주파 신호 기억 장치에 대한 설계가 가능해 졌다. 본 논문에서는 주파수 대역이 600MHz 이상 되는 광대역 디지털 고주파 복제회로를 사다리 회로를 이용하여 설계하고 그 결과를 모사하였다.

• 전기의세계
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• 제25권6호
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• pp.65-68
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• 1976

For the RIV characteristics test of power apparatus, an indoor measuring system of radio influence voltage was set up and by means of this measuring unit SIV characteristics on the 7$^{1}$2/" pin-type domestic insulators were examined. According to the test data, RIV values of all the test pieces exceeded the maximum permissible level at 10kV applied voltage. The electrical resistivity of domestic semi-conductive glaze as good as importedone but un-uniformity of coating is turned out to be a main cause of failure.lure.

• 전자공학회논문지A
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• 제30A권9호
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• pp.1-5
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• 1993

The surge impedance of grounding systems must be accurately computed for a safe grounding design. Specifically, the case of radio relay station in a mountaintop region is required special design method using transient analyses. To approach these design objectives, this paper presents an algorithm to compute the surge impedance of two or more grounding systems using the Laplace Transform technique and deals with the analysis of the transient characteristics on grounding systems. Also, simulation results are compared with the measured data to prove the validity of the algorithm.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2006년도 하계종합학술대회
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• pp.65-66
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• 2006

In this paper, we designed and fabricated a broadband antenna for EMI site validation above 1 GHz. To develop the antenna which is satisfied omni-directional radiation pattern and broadband characteristics required by CISPR, we designed biconical type with cylindrical load. The developed antenna has good characteristics of the radiation patterns and VSWR<2 the frequency range from 1 GHz to 18 GHz.

• 천문학논총
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• 제14권1호
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• pp.39-45
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• 1999

We have carried out measurements of 1.2-1.6GHz radio interferences around Seoul Radio Astronomy Observatory located in the campus of Seoul National University. We received interference signals using a pyramidal horn antenna and measured its power using a spectrum analyzer with 1MHz resolution after $\~60dB$ amplification. In order to check the spatial characteristics, we made observations at every $30^{\circ}$ in azimuth at elevation of $30^{\circ}\;and\;60^{\circ}$. Also, in order to check the temporal characteristics, we repeated the all-sky observations five times at every six hours. The results may be summarized as follows: (1) There are strong $({\geq}-20dBm)$ interferences between 1.2 and 1.4GHz. Particularly strong interferences are observed at 1.271 and 1.281GHz, which have maximum powers of -0.34dBm and -0.56dBm, respectively. (2) The characteristics of the interferences do not depend strongly on directions, although the interferences are in general weak at high elevation and in east-west direction. (3) The interferences appear for a very short $(\leq0.01s)$ period of time, so that the average power is much smaller than the maximum power. Strong interferences with large $(\leq-49.0dBm)$ average power have been observed at 1.271, 1.281, 1.339, and 1.576GHz. At these frequencies, the interferences appear repeatedly with a period of $\leq0.1s$ By analyzing the observed power, we find that, for the strongest 1.271GHz interference, the average intensity is $-171dBW/m^2/Hz$ and that the maximum intensity is $-122dBW/m^2/Hz$. If this interference is delivered to the detector without any shielding, then its power would be much greater than the rms noise of a typical line spectrum. Therefore, it is important to shield all the parts of receiver carefully from radio interferences. Also, without appropriate shielding, the sensitivity of a receiver could be limited by the interference.