• Journal of the Korea Institute of Information and Communication Engineering
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• v.9 no.8
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• pp.1780-1786
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• 2005

The phase error generated in the transmission system affects the performance of digital transmission signal. The phase error are generated by random phase noise and tracking phase error due to denier phenomenon. In the mobile satellite communication system that generates the doppler frequency, which is a system with a movement, the proper system phase noise spectrum should be designed based on analyses for phase noise and static phase error effects. Based on the analyses of the doppler frequency and the phase error for bilateral satellite communication system providing an asynchronous service, the phase noise spectrums for the mobile satellite communication are designed in this paper. Also, the available transmission services under the less doppler effect are proposed and the proper signal source units for a required transmission system can be designed under the proposed system phase noise spectrum.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2009.05a
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• pp.605-608
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• 2009

It is necessary to estimate the Doppler spectrum for each range cell for the extraction of useful information from the return echoes in radar systems used for the remote sending purpose. However, The conventional spectrum estimation method, FFT(Fast Fourier Transform), called the Doppler filter bank, causes the frequency resolution problem if the dwell time is relatively short. This short acquisition time also spreads the side lobe levels of return echoes further, resulting in difficulties for the discrimination of weak target signals included in relatively strong target echoes. Therefore, in this paper, the efficient Doppler spectrum estimation methods are compared and investigated through the parameter spectrum estimation in the time domain to overcome these problems.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2007.10a
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• pp.853-856
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• 2007

A weather radar extracts the weather information from the return echoes which consist of scattered electromagnetic wave signals from rain, cloud and dust particles, etc. The acquisition of accurate weather information depends on the operation environment which include the Doppler weather signal and ground clutter characteristics. Since the conventional symmetric weather Doppler model does not represent the measurements in real situations, the improved model is suggested to describe the skewness in the Doppler spectrum model. Using the suggested model, many various weather signals can be simulated to verify the accuracy of signal processing algorithms and the reliability of the extracted weather information

• Journal of the Korea Institute of Information and Communication Engineering
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• v.13 no.9
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• pp.1753-1759
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• 2009

A weather radar as one of the remote sensing devices to analyze the weather phenomena receives the return echoes which consist of scattered electromagnetic wave signals from rain, cloud and dust particles, etc. These received Doppler weather spectra are analyzed to extract the various characteristic weather information. The mean wind velocity is one of the important weather parameters which can be obtained by a weather radar ed it may be useful in the prevention of weather hazards occurred by the abrupt shift of wind in small geographical scales such as microbursts. It is usually estimated by pulse pair method which is considered to be reliable and very efficient in the computational requirement. However, there are some problems in the accurate estimation of the mean velocity if Doppler spectra of weather signals appear to be asymmetric gaussian or multi-peak spectra. Therefore, in this paper, the problems in the mean estimation of asymmetric Doppler spectra are analyzed and the improved method is suggested.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.24 no.12B
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• pp.2292-2297
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• 1999

Some observed weather spectra show that nearly 25% of weather spectra are seriously skewed and can not be considered to be symmetric. However, the conventional pulse pair method was derived and has been evaluated under the assumption that the weather spectrum is symmetric and narrow. This means that the conventional pulse pair method may need reevaluation. Therefore, this paper analyzed the bias errors of pulse pair estimates in the skewed spectra. The bias errors of pulse pair mean estimates are more serious comparing with the pulse pair width estimates. In this paper, the poly-pulse pair method is suggested to reduce these bias errors of mean estimates. It was shown that the mean bias errors can be reduced remarkably using the newly suggested poly-pulse pair method.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.20 no.9
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• pp.1641-1648
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• 2016

A weather radar estimates Doppler frequency and width of Doppler spectrum from the received weather signal which represents the return echoes from rain or dust particles in a corresponding area. These estimates are very important parameters since they are directly related to precipitation, wind velocity and degree of turbulence. Therefore, these estimated values should be highly reliable to obtain accurate weather information. However, the echoes of a weather radar include both the weather signal and the clutter which occurred from ground reflection or moving objects, etc. The existence of the clutter in the echoes may cause serious errors in the estimation of weather-related parameters. Therefore, in this paper, models are developed to represent the weather signal and the clutter for the purpose of analyzing estimation errors caused by the strong clutter echoes. Using these models, various return echoes according to the weather signal and clutter power are simulated to analyze the effects of the clutter.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.21 no.9
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• pp.1818-1825
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• 2017

An Acoustic Doppler Current Profiler(ADCP) measures the current velocity and analyzes the degree of turbulence using Doppler effects of ultrasonic waves. Therefore, the autocorrelation or FFT spectrum estimates are obtained for extraction of current velocity in each spatial region. However, if the correlation method does not satisfy the assumption that the return signal spectra are symmetric Gaussian, the large bias errors can occur. Also, the accurate estimation of autocorrelation or FFT spectrum is difficult due to the short acquisition interval when the rapid changes of current velocity occur. Thus, in this paper, the estimation method of the autoregressive spectrum peak is suggested for the accurate current velocity measurement of both symmetric and asymmetric spectra. It is shown that estimation quality can be improved using the suggested method comparing with the conventional methods. Many return signals under the various environment are simulated and the results are compared and analyzed for evaluation of the suggested method.

• Proceedings of the Korea Water Resources Association Conference
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• 2005.05b
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• pp.367-371
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• 2005

본 논문에서는 수리실험을 통해 개수로의 바닥 조건에 따른 평균흐름 및 난류구조, 그리고 고유구조의 특성을 연구하였다. 레이저 도플러 유속계를 이용하여 2차원 순간속도를 측정하였다. 측정된 평균유속, 레이놀즈응력, 난류강도, 와점성계수, 혼합 길이 등의 난류량을 기존에 제시된 경험식과 비교하였으며 기존 연구 결과와 유사함을 확인하였다. 사분면 기법을 이용하여 개수로 흐름의 고유구조를 살펴본 결과, 분출 및 쓸기 현상의 발생 확률이 다른 상호작용에 비해 지배적임을 확인하였다. 고속 푸리에 변환을 통한 스펙트럼 분석을 통하여 에너지 폭포 현상 및 난류 와의 미시 및 거시 특성크기를 파악하였다.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• v.9 no.1
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• pp.735-738
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• 2005

The phase error in the digital transmission system are generated by random phase noise and tracking phase error due to doppler phenomenon. In the mobile satellite communication system that generates the doppler frequency, which is a system with a movement, the proper system phase noise spectrum should be designed based on analyses for phase noise and static phase error effects. Based on the analyses of the doppler frequency and the phase error for bilateral satellite communication system providing an asynchronous service, the phase noise spectrums for the mobile satellite communication are designed in this paper. Also, the available transmission services under the less doppler effect are proposed and the proper signal source units for a required transmission system can be designed under the proposed system phase noise spectrum.

• The Journal of the Acoustical Society of Korea
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• v.1 no.1
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• pp.70-75
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• 1982

본 논문에서는 이차원스펙트럼 분석기를 구성하여 진동 파라미터들을 추정하고 기존 방법인 Power Spectrum 방법과 비교 검토하여 이차원스펙트럼이 gaussian noise를 제거하기 때문에 유효함을 알 수 있었다.