• 한국통신학회논문지
• /
• 제31권2A호
• /
• pp.187-193
• /
• 2006

Multicarrier systems has major shortcomings due to the large numbers of subcarrier. One of the shortcomings is the high peak-to-average power ratio(PAPR), which causes nonlinearity distortion in the transmitter, and degrades the performance of the system significantly. Partial transmit sequence(PTS) is one of the best approaches that can significantly improve the statistics of the PAPR of an orthogonal frequency division multiplexing(OFDM) signal. Guided scrambling(GS) is an extension of self-synchronizing scrambling. It is also capable of guiding the scrambling process to produce a balanced encoded bit stream. In this paper, we propose a sub-optimal algorithm to optimize the phase factor in PTS. In addition, we integrate GS coding with this method. The proposed Hybrid algorithm can get much more PAPR reduction at the expense of incur a few error extension and do not require transmission of side information.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 2001년도 하계학술대회 논문집
• /
• pp.609-612
• /
• 2001

To investigate the magnetic field distribution of power line, we used amorphous wire sensor. And we discuss extremely low frequency magnetic field distribution dependent upon arrangement of power line and shielding pipe made from iron or alumimum materials by both measurement and FEM(Finite Element Method) analysis. Appling current of single phase 60 [Hz] 15 [A] is supplied to copper wire coated enamel resign. As the results, we confirmed that linear characteristics of amorphous wire sensor is very excellent and measurement value agrees with FEM calculation. Magnetic field distribution due to shielding materials is changed by permeability and conductivity.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 1997년도 춘계학술대회 논문집
• /
• pp.229-232
• /
• 1997

A free space transmission method using standard gain horn antennas in the frequency range from 9.0 to 10.5GHz is applied to determine the dielectric properties of grain such as rough rice, brown rife and barley. The dielectric constant and loss factor, which depend on the moisture content of the wetted grain are obtained from the measured attenuation and phase shift by vector network analyzer. The effect of density fluctuation, which is an important parameter governing the dielectric properties of grain, on the dielectric constant and loss factor is presented. A new density-independent model in terms of measured attenuation and moisture density is proposed for reducing the effects of density fluctuation on the moisture content measurement.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2006년도 제37회 하계학술대회 논문집 A
• /
• pp.268-269
• /
• 2006

Auto-synchonizer is important device to match the voltage, frequency, phase of the generating system to those factors of the transmission line, when the synchronous generator is operated. There were few or no incidents by Synchronization failure at Hapcheon hydraulic power plant, since it was built in 1989. but incidents by Synchronization failure have often happend lately. From now, let's improve the efficiency on the maintenance of generating equipment by studying about the cause and the method for this problem by comparing with the set point of each device of synchronizing system.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2005년도 제36회 하계학술대회 논문집 D
• /
• pp.3001-3003
• /
• 2005

이 논문에서는 OFDM(orthogonal frequency division multiplexing) 통신 시스템에서 고려해야할 중요한 문제 중의 하나인 PAPR(peak to average power ratio) 문제를 다루었다. SLM(selected mapping) OFDM 시스템을 기반으로 구현하였고, PAPR을 줄이기 위한 방법으로 새로운 위상 가중치를 곱하는 방법을 제안하였다. 여기서는 여러 가지 방법들(PSK, QPSK, 랜덤)로 위상 가중치를 발생시켰고, 발생된 위상 가중치를 병렬 조합으로 적용하여, 최저의 PAPR을 가져오는 값을 선택했다. 실험결과에서, 단일의 위상 가중치만을 곱하여 사용할 때 보다 위상 가중치를 복합적으로 사용했을 때 큰 PAPR 감소를 보임으로서, 제안된 방법의 우수성을 보였다. 그러나 아직 해결해야할 것들 중에서, 여러가지 위상 가중치를 사용함에 따른 시스템 복잡도가 증가하는 문제점이 존재한다. 본 연구에서 제안하는 방법은 비록 복잡도의 증가라는 단점을 가지고 있지만, 성능면에서의 향상은 커다란 장점이다.

• 전기학회논문지
• /
• 제59권5호
• /
• pp.966-971
• /
• 2010

An adaptive state observer is presented for a class of LTI systems that have a sinusoidal disturbance in the measurement output. Adaptation rules are developed for identifying the unknown sinusoidal disturbance signal from the system output. For the application of the identification result to the state estimation problem, the sinusoidal signal with arbitrary initial phase has been considered in this paper. In order to test the performance of proposed algorithm, comparative computer simulations have been carried out with an existing robust observer. The simulation results show the effectiveness of the proposed method.

• 대한전자공학회논문지
• /
• 제16권1호
• /
• pp.14-21
• /
• 1979

본 논문에서는 FSK 통신을 사용한 전자계산기의 On-Line 계통에서의 오차를 연구하였으며 수신측의 발광주파수 피상을 송신측에 일치시키는 회로를 설계함으로써 4 % 이내의 주파수 편이에서도 동작이 가능하게 하였다. 또한 On-Line 계통에서 비트 오차를 계산하기 위하여는 Micro-processor를 사용하였고, 발생된 대부분의 오차는 FSK 통신계통에 의한 것이었으며, 본 연구에서 설계한 방식을 사용함으로써 완위레지스터에서 마이브로프로서로 입력되는 오차는 매우 적게 되었다.

• ETRI Journal
• /
• 제42권3호
• /
• pp.333-340
• /
• 2020

We consider a hybrid combiner design for downlink massive multiple-input multiple-output systems when there is residual inter-user interference and each user is equipped with a limited number of radio frequency (RF) chains (less than the number of receive antennas). We propose a hybrid combiner that minimizes the mean-squared error (MSE) between the information symbols and the ones estimated with a constant amplitude constraint on the RF combiner. In the proposed scheme, an iterative alternating optimization method is utilized. At each iteration, one of the analog RF and digital baseband combining matrices is updated to minimize the MSE by fixing the other matrix without considering the constant amplitude constraint. Then, the other matrix is updated by changing the roles of the two matrices. Each element in the RF combining matrix is obtained from the phase component of the solution matrix of the optimization problem for the RF combining matrix. Simulation results show that the proposed scheme performs better than conventional matrix-decomposition schemes.

• 천문학논총
• /
• 제25권2호
• /
• pp.31-49
• /
• 2010

Next to Paper I (Jeon 2009a), time-series BV CCD images of the open cluster M38 were taken for 4 nights on December, 2009. The observations have been carried out for total 27 nights. In addition to the 20 variable stars in the Paper I, the discovery of 44 new variable stars has been presented in this paper: $6{\delta}$ Scuti stars, $2{\gamma}$ Doradus stars, 18 eclipsing binaries and 18 semi-long periodic and/or slow irregular type variable stars. For the V photometry of the ${\delta}$ Scuti and ${\gamma}$ Doradus stars, multi-frequency analysis was performed using the Discrete Fourier Transform and linear least-square fitting. The period search for the eclipsing binaries and the semi-long periodic and/or slow irregular type variable stars was performed by phase fitting method. As a result, the periods for 23 variable stars among the 44 ones were defined.

• 한국전산유체공학회:학술대회논문집
• /
• 한국전산유체공학회 2003년도 The Fifth Asian Computational Fluid Dynamics Conference
• /
• pp.291-293
• /
• 2003

This paper deals with a thrust generation of flapping-airfoil by dynamic stall. From many other previous research results, phase angle $ between pitching and plunging mode of flapping motion must be 90 deg. to satisfy maximum propulsive efficiency. In this case, leading edge vortex is relatively small. This phenomenon is related dynamic stall. So preventing leading edge vortex induced by dynamic stall guarantees maximum propulsive efficiency. But, in this paper we insist the leading edge vortex yields quite a positive influence on thrust generation and propulsive efficiency. In order to certify our opinion, pitching and plunging motions were calculated with the parameter of amplitude and frequency by using the unsteady, incompressible Navier-Stokes flow solver with a two-equation turbulence model. For more efficient computation, it is parallelized by MPI programming method.