• 대한전기학회논문지:시스템및제어부문D
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• 제54권1호
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• pp.56-60
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• 2005

In the power-line communication(PLC) systems, the power line is a wired medium. However, the power line channel has the multi-path fading characteristics like the wireless channel in the wireless communication systems because it has the signal reflection and divergence by the impedance mismatching between many branch lines and loads. So the analysis of the multi-path characteristics is very important, and it has been doing by the several measurement methods for the impulse response between the transmitter and the receiver. PN sequence method has originally been used as a wideband impulse response measurement mettled for wireless channel, but it is recently being applied to not only the wireless channel but also the wired channel like the power line channel. This method is more useful and effective for the long distance communication channel like the medium voltage power distribution line with the multi-paths[1]. In this thesis, we have measured impulse response for the medium voltage power distribution line channel by the wideband measurement method using PN sequence, analytically studied the measured data and presented the results.

• 대한전자공학회논문지TC
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• 제42권12호
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• pp.165-170
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• 2005

본 논문은 임펄스 전파 채널 측정에 있어서, 사용된 초광대역 (Ultra Wideband) 안테나가 시간 및 주파수 영역에서 임펄스 전파 채널에 미치는 영향을 기술하고자 한다. 임펄스 전파 채널에서의 초광대역 안테나의 영향을 해석하기 위해, 우선 초광대역 안테나의 임펄스 응답을 구하였고, 이를 이용하여 초광대역 안테나의 영향이 배제된 임펄스 전파 채널 해석 방법을 제시하였다. 이론적 증명을 위해, 임펄스 전파 채널 측정을 위한 변형된 초광대역 코니컬 모노폴 안테나를 설계, 제작하였고 무반향 반사실에서의 전달 특성을 측정하여 초광대역 안테나의 임펄스 응답을 도출하였다. 또한, 임펄스 전파 채널 상에서의 초광대역 안테나에 대한 영향을 해석하기 위해, 무반향 반사실에서 다중경로 환경을 만들어 주파수 영역에서 벡터 회로망 분석기를 사용하여 전달 특성을 측정하였다. 주파수 영역에서 측정된 데이터는 신호 처리 과정을 거쳐 시간 영역의 신호로 변환하였다. 측정된 결과로부터, 안테나의 특성이 임펄스 전파 채널에 영향을 미침을 확인하였다. 또한, 초광대역 안테나의 임펄스 응답을 사용하여 순수하게 다중경로 채널에 의한 임펄스 응답을 구하였다.

• 전자공학회논문지A
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• 제32A권10호
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• pp.1-7
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• 1995

In this paper, the properties of autocorrelation function of binary sequences are investigated. From these properties, the binary sequences which can be used for measurement of impulse response on fading channel are found by computer search. A receiver which can measure impulse response by use of these binary sequences is devised. This devised measurement system produces zero values of autocorrelation function for the all delays except zero sight.

• Journal of Communications and Networks
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• 제1권3호
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• pp.166-181
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• 1999

The object of this paper is to investigate the influence of antenna pattern on indoor radio channel characteristics. Different from previous works where this analysis was carried out at a fixed frequency using different antennas, in the present paper (where measurements were taken in a wide frequency range) the variation of the radiation pattern was caused by two factors: the change of the radiation pattern when the same antenna was used at different frequenicies and the use of different type of antennas. To carry out this analysis, frequency domain measurements of the indoor radio channel at 1 GHz, 5.5 GHz, 10 GHz and 18 GHz were collected. Measurements were taken using a network analyzer. Serveral re-alizations of the channel transfer function were obtained varying, for each measurement, the positon of the transmitter and keep-ing the receiver fixed. Estimate of the channel impulse response was obtained from the Inverse Fourier Transform (IFT) of the fre-quency response. The measurements were performed in an office enviroment with mostly metallic walls and inner separations. The obtained data were elaborated to obtain the power versus distance relationship, the Cummulative Distribution Functions(CDFs) of rms Delay Spread(DS) and of the 3 dB frequency correlation band-width. Finally, the 3 dB width of the frequency correlation func-tion has been empirically related to the inverse of the rms DS of the impulse response.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2008년도 하계종합학술대회
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• pp.12-13
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• 2008

In this paper, we propose a performance evaluation method for MIMO antennas through channel sounding. From measurement data, the complex channel gain, delay, angle of arrival, and angle of departure of each multipath are estimated. Using these estimates, the MIMO channel impulse response adopting various types of antennas are constructed by replacing the array response vectors, considering antenna patterns and correlation among antenna elements. Comparisons are made in terms of the metrics computed from the impulse responses.

• 대한의용생체공학회:의공학회지
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• 제27권5호
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• pp.229-236
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• 2006

The acoustic field analysis method is the superior calibration method for rectifying the ultrasonic probe sensitivity. This method also can be applied to evaluate the probe performance in clinical fields without numerical analysis and precise measurements. In this paper, we propose the method of acoustic field pattern analysis with probe channel division for the evaluation of diagnostic ultrasound probe characterization. In order to verify our purpose, we performed a set of experiments. We measured the acoustic-field pattern of the three inferiority probes by channel division to evaluate an acoustic field distribution and impulse response characteristics. By comparing the results of acoustic field measurement method with that of conventional method such as impulse response and live image test for linear array probes, it is demonstrated that the ultrasound field measurement method is more effective then conventional method in detection of defective elements.

• 대한전자공학회논문지TC
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• 제42권9호
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• pp.19-28
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• 2005

본 논문에서는 실제 아파트 환경에서 2000번의 주파수 응답에 의한 통계적 UWB 실내 채널 모델을 연구하였다. 측정은 서로 다른 방, 서로 다른 위치에서 이루어 졌으며, 실험 결과를 통해 채널의 전파특성을 이론적으로 설명하였다. Time-domain상에서 측정할 수 있는 channel impulse response (CIR)와 frequency-domain상에서 측정할 수 있는 channel transfer function (CTF) 측정방법을 제안하였다. 측정데이터를 통해서 CIR과 CTF를 비교하여 분석하였고, 통계적 경로손실 모델 또한 제안하였다. 신호 대역은 10MHz에서 8.010Hz까지 사용하였다. 측정결과를 통해 time-domain상에서 확인할 수 있는 maximum excess delay, mean excess delay, ms delay spread를 나타내었다. 송신기와 수신기에는 전방향의 biconical 안테나를 사용하였다. 또한 제안된 아파트 환경에서의 채널 모델은 UMB용 안테나 특성이 포함된 결과이다.

• ETRI Journal
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• 제34권6호
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• pp.858-868
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• 2012

In this paper, stochastic models for the cross-correlation of multiple channels are established based on measurement data collected using a wideband multiple-input multiple-output relay Band Exploration and Channel Sounder system at 3.7 GHz. We propose models for the cross-correlation characteristics of large-scale parameters (LSPs) between two links, that is, the base station and mobile station (MS) link and the relay station and MS link. The LSPs include shadow fading, Rician K-factor, delay spread, angle spread of arrival, and angle spread of departure. Furthermore, models are established for the cross-correlation of the small-scale fading in the impulse responses of two links. The statistics of these model parameters are investigated as functions of geometrical features of the multilink. They are extracted from a large amount of cross-correlation observations, which are obtained in three measurement sites along more than one hundred measurement routes. These models can be used together with the standard single-link channel models for the generation of correlated components, for example, path clusters, in two separate channels.

• 한국음향학회지
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• 제38권5호
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• pp.494-510
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• 2019

수중음향통신시스템의 모뎀이나 채널 코딩 설계를 위한 채널 매개변수는 임펄스 응답, 지연 확산, 산란함수, 도플러 확산, 상관 대역폭, 주파수 선택적 페이딩, 상관 시간 및 시변 진폭 페이딩의 통계적 분포 함수 등이다. 이들 매개 변수들은 주어진 해양 음향 조건에서 수층의 음속 구조, 플렛폼의 운동이나 해면의 거칠기에 영향을 받는다. 본 논문에서는 송수신기 고정 천해 수중음향통신 채널에 대한 페이저 기반의 채널 모델과 모의실험 및 채널 매개변수들의 측정과 분석 방법을 제시하고 천해의 실험 자료를 이용하여 이들 매개변수들을 해석하였다. 송수신기 거리가 300 m와 600 m에 대한 이들 매개 변수들은 직접파, 산란 성분을 갖는 해면 반사파 및 해저 반사파로 구성되는 3개 다중 경로에 의해 그 특징이 결정됨을 보인다. 연구의 결과는 천해 고정 시스템의 채널 모델 방법, 채널 매개변수들의 측정과 분석 방법 및 시스템 설계와 성능평가 방법을 제시한다.

• 대한전기학회논문지
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• 제40권12호
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• pp.1290-1295
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• 1991

The paper presents the measurement results on the parameters affecting the breakdown mechanism of a large air spacing under switching impulse voltages. Measured parameters are the velocities of leader channels, predischarge currents, electric charges injected into the rod-plane air gap and electric field intensities on the plane. For the 3m air gap under switching impulse voltages, the velocities of leader channel have been measured to be of 1cm/x10S0-6Ts - 5cm/x10S0-6Ts, electric field intensity of 2kv/cm, predischarge current of 1.2-1.6A, the charges injected into the air gap of 11-40x10S0-6TC for 400-887kV impulse voltages.