• Title/Summary/Keyword: 위상 민감도

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Analysis of Phase Noise Effects in OFDM Systems Using Transceiver Diversity (송수신 다이버시티를 적용한 다중 반송파 시스템에서의 위상잡음 영향 분석)

  • Lee, Jong-Gil
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.11 no.2
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    • pp.280-286
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    • 2007
  • In this paper, the phase noise effects of OFDM transceiver diversity systems were analyzed. Since OFDM communication system is very sensitive to phase noise, the system performance may degrade seriously due to the increase of subcarrier interferences and system noise. Therefore, the phase noise model was suggested and its distribution and power were varied to investigate the effects of phase noise on the system performance. The degree of the system performance degradation depends on the specific diversity structures of transceiver systems. Here, the performances of OFDM systems with two antennas transceiver diversity were analyzed and compared with that of systems with only transmission diversity and without diversity as the phase noise characteristics varied.

A Fast sensitivity computation technique for an efficient and accurate contingency analysis (능률적이고 정확한 상정사고 해석을 위한 민감도 산출기법 연구)

  • Lee, Seung-Chul;Moon, Woon-Chul;Oh, Hae-Jin;Kwon, Byeong-Gook
    • Proceedings of the KIEE Conference
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    • 2004.11b
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    • pp.75-77
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    • 2004
  • 상정사고 해석의 경우 수많은 상정사고를 실시간에 해석하기 위하여 전력조류계산 결과로 얻어진 Jacobian의 역행렬이 포함하고 있는 민감도 정보를 이용하는 경우가 많다. 이 경우 각종 상정사고 후의 각 모선전압과 전압의 위상각과 같은 상태변수를 선형적으로 신속히 계산할 수 있는 장점이 있는 반면에 송전선로 고장과 같이 계통구성이 변하는 상정사고의 경우에는 계산결과 얻어지는 상태변수 값들의 오차가 커져 상정사고 해석 결과가 부정확해지는 문제점이 있다. 이때 보다 정확한 상태변수 값들을 계산하기 위해서는 탈락한 송전선로를 반영하여 Jacobian을 재구성하고 그 역행렬을 계산하여야한다. 본 논문에서는 특히 민감도를 이용한 상태변수 값의 선형 계산에서 오차가 커지는 문제점이 있는 송전선로 고장의 경우 계통의 구조 변화를 반영한 Jacobian의 역행렬을 별도로 계산하지 않고 기본 케이스 Jacobian의 역행렬을 그대로 이용하여 간단히 구하는 방법을 제시함으로서 보다 빠르고 정확한 상정사고 해석을 할 수 있는 기법에 대해 제안하였다. 제안한 방법은 뉴잉글랜드 39 모선 계통에 적용하여 그 효과를 입증하였다.

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Topology Optimization of a Vibrating System of Rigid and Flexible Bodies for Maximizing Repeated Eigenfrequencies (중복 고유 진동수를 갖는 진동하는 강체-유연체 계의 위상최적설계)

  • Ahn, Byungseong;Kim, Suh In;Kim, Yoon Young
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.40 no.4
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    • pp.363-372
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    • 2016
  • When a system consisting of rigid and flexible bodies is optimized to improve its dynamic characteristics, its eigenfrequencies are typically maximized. While topology optimization formulations dealing with simultaneous design of a system of rigid and flexible bodies are available, studies on eigenvalue maximization of the system are rare. In particular, no work has solved for the case when the target frequency becomes one of the repeated eigenfrequencies. The problem involving repeated eigenfrequencies is solved in this study, and a topology optimization formulation and sensitivity analysis are presented. Further, several numerical case studies are considered to demonstrate the validity of the proposed formulation.

The image construction of the surface and subsurface defects using complex amplitude of the reflected ultrasonic signals from the solid (초음파 반사신호의 복소 진폭을 이용한 교체 내부 결함의 영상 구조)

  • Kim, Hyun;Lim, Ho;Kim, Ki-Yeoul;Koo, Kil-Mo
    • The Journal of Information Technology
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    • v.4 no.2
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    • pp.129-136
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    • 2001
  • Most of the acoustic microscopes have been constructed acoustic image by simply measuring the amplitude of the reflected signal from the specimen. This method fails to produce images of good quality because the change in amplitude is not sensitive enough to specimen with fine variation. In this paper, we have been constructed the acoustic microscope system which has been able to measure simultaneously the amplitude and phase of the reflected ultrasonic signal. And also we have been constructed the amplitude and phase images for the 500 won coin as a sample and the alumium spacimen with internal round defect, and compared and analyzed these images. In expermental result, the phase image have shown better sensitive than the amplitude image and given better contrast for the micro height variation of specimen. It will be expected that the phase image can be used as an additional bit of information to improve ambiguituities in amplitude image on nondestructive testing for specimen with fine variation.

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Reliability-Based Topology Optimization Using Performance Measure Approach (성능함수법을 이용한 신뢰성기반 위상 최적설계)

  • Ahn, Seung-Ho;Cho, Seon-Ho
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.23 no.1
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    • pp.37-43
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    • 2010
  • In this paper, a reliability-based design optimization is developed for the topology design of linear structures using a performance measure approach. Spatial domain is discretized using three dimensional Reissner-Mindlin plate elements and design variable is taken as the material property of each element. A continuum based adjoint variable method is employed for the efficient computation of sensitivity with respect to the design and random variables. The performance measure approach of RBDO is employed to evaluate the probabilistic constraints. The topology optimizationproblem is formulated to have probabilistic displacement constraints. The uncertainties such as material property and external loads are considered. Numerical examples show that the developed topology optimization method could effectively yield a reliable design, comparing with the other methods such as deterministic, safety factor, and worst case approaches.

Phase Noise Analysis and Suppression Algorithm for OFDM-Based 60GHz WLANs (OFDM 기반의 60GHz WLAN을 위한 위상잡음 해석과 위상잡음 억제 알고리즘)

  • Kim Han-Kyong;Ahn Kyung-Seung;Baik Heung-Ki
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.30 no.12C
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    • pp.1248-1255
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    • 2005
  • We investigate the OFDM-based wireless LAN systems operating in the 60 GHz frequency band as part of the fourth-generation (4G) systems. The 60 GHz band is of much interest since this is the band in which a massive amount of spectral space has been allocated worldwide for dense wireless local communications. This paper gives an overview of 60 GHz bandchannel characteristics and an effect on phase noise. The performance of OFDM system is severely degraded by the local oscillator phase noise, which causes both common phase error and inter-carrier interference. In this paper, we apply phase noise suppression (PNS) algorithm that is easy for implementation to OFDM based 60 GHz wireless LAM system and analyze the SER performance. In case of using the PNS algorithm, SER performance is improved about 6dB, 7.5dB, respectively in 16, 64-QAM.

Nanoaperture Design in Visible Frequency Range Using Genetic Algorithm and ON/OFF Method Based Topology Optimization Scheme (유전알고리즘 및 ON/OFF 방법을 이용한 가시광선 영역의 나노개구 형상의 위상최적설계)

  • Shin, Hyun Do;Yoo, Jeonghoon
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.37 no.12
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    • pp.1513-1519
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    • 2013
  • A genetic algorithm (GA) is an optimization technique based on natural evolution theory to find the global optimal solution. Unlike the gradient-based method, it can design nanoscale structures in the electric field because it does not require sensitivity calculation. This research intends to design a nanoaperture with an unprecedented shape by the topology optimization scheme based on the GA and ON/OFF method in the visible frequency range. This research mainly aims to maximize the transmission rate at a measuring area located 10nm under the exit plane and to minimize the electric distribution at other locations. The finite element analysis (FEA) and optimization process are performed by using the commercial package COMSOL combined with the Matlab programming. The final results of the optimized model are analyzed by a comparison of the electric field intensity and the spot size of near field with those of the initial model.

Analysis of Phase Noise Effects in OFDM Transmit Diversity Systems (OFDM 송신 다이버시티 시스템에서의 위상잡음 영향 분석)

  • Lee, Jong-Gil
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.10 no.2
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    • pp.243-249
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    • 2006
  • In this paper, the phase noise effects of OFDM transmission diversity systems were analyzed. Since OFDM communication system is very sensitive to phase noise, the system performance may degrade seriously due to the increase of subcarrier interferences and system noise. Therefore, The phase noise model was suggested and its distribution and power were varied to investigate the effects of phase noise on the system performance. The degree of the system performance degradation depends on the specific diversity structures of transmission systems. Here, the performances of OFDM systems with two and three antennas transmission diversity were analyzed and compared with that of systems without transmission diversity as the phase noise characteristics varied.

An Efficient ICI Self-Cancellation Method with Frequency Offset and Phase Noise in OPDM Systems (OFDM 시스템에서 주파수 오차와 위상 잡음에 의한 ICI를 제거하기 위한 효율적인 자가상쇄 기법)

  • Park, Jeong-Hwan;Kim, Hyung-Myung
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.34 no.2A
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    • pp.155-163
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    • 2009
  • OFDM System is a promising transmission technique due to its spectral efficiency But, a major disadvantage of the OFDM system is its sensitivity to frequency offset and phase noise that makes intercarrier interference (ICI), which degrades the system performance severely The ICI self-cancellation method has a good performance with frequency offset or phase noise. This paper proposed the N/2 spacing data-conjugate method that works well in large frequency offset and phase noise (normalized frequency offset=0.2-0.4, phase noise standard deviation=about lodes). Also, an efficiency ICI cancellation method using pilot was proposed. Simulation results confirm that performance of the proposed scheme is better than conventional schemes.