• Journal of Advanced Navigation Technology
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• v.23 no.2
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• pp.142-150
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• 2019

Muzzle Velocity is one of the most important measurement items for evaluation of ammunition. The muzzle velocity is defined as the velocity when the projectile leaves the muzzle. Particularly, since the muzzle velocity is closely related to the performance of the propellant, precise measurement of muzzle velocity is required. Doppler radar is used to measure the muzzle velocity, but the quality of Doppler radar signal depends on the test site environment. In this paper, a method to remove the clutter that degrades the signal quality of Doppler radar by improving the structure of the test site and the signal processing method is suggested. For the application of the improved signal processing method, a program for acquiring Doppler radar's raw Doppler data was created. Statistical verification of the velocity data obtained through the improvement of the test site structure and signal processing method proved that the proposed method is effective for the removal of clutter as compared with the existing method.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.16 no.7 s.112
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• pp.677-682
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• 2006

In the case of aeroacoustic test in windtunnel, measurement accuracy is reduced by not only Doppler effects but also by the microphone self noise due to airflow and high turbulence in the wall boundary layer. Microphone array measurements can be easily utilized for the solutions of these problems. In this paper, geometrical optics approach and diagonal term elimination of cross spectral matrix was introduced to the de-dopplerization and self noise reduction methods for the microphone array measurement. For the validation, beamforming tests for sinusoidal point source were performed in the closed type test section of windtunnel, and their performances of beam width and sidelobe rejection were significantly improved.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.11a
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• pp.822-825
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• 2005

In the case of aeroacoustic test in windtunnel, measurement accuracy is reduced by not only Doppler effects but also by the microphone self noise due to airflow and high turbulence in the wall boundary layer. Microphone array measurements can be easily utilized for the solutions of these problems. In this paper, geometrical optics approach and diagonal term elimination of cross spectral matrix was introduced to the de-dopplerization and self noise reduction methods for the microphone array measurement. For the validation, beamforming tests for sinusoidal point source were performed in the closed type test section of windtunnel, and their performances of beam width and sidelobe rejection were significantly improved.

• Proceedings of the IEEK Conference
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• 2000.09a
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• pp.479-482
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• 2000

다중경로 채널의 시변 특성은 OFDM(orthogonal frequency division multiplexing) 신호의 직교성을 파괴시키며 이는 인접 채널간 간섭(ICI: interchannel interference)을 발생시켜 도플러 주파수에 비례하는 오류를 발생시킨다. 본 논문에서는 채널 시변의 원인을 주파수 옵셋과 도플러효과로 규정하고, 주파수 옵셋을 보정하기 위해 기존의 선형보간법(LI: linear interpolation method)대신 선형위상보간법(LPI: linear phase interpolation)과 도플러효과에 의한 ICI 를 제거하기 위해 기존의 주파수영역 등화기법보다 효과적인 시간영역 등화기법을 제안한다. 제안된 기법이 주파수 옵셋이 있는 시변 다중경로 페이딩 환경에서 OFDM 시스템에 적합함을 컴퓨터 모의실험을 통해 확인한다.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 1999.11b
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• pp.161-165
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• 1999

다중경로 채널의 시변 특성은 OFDM(orthogonal frequency division multiplexing) 신호의 직교성을 파괴시키며 이는 인접 채널간 간섭(ICI: inter channel interference)을 발생시켜 도플러 주파수에 비례하는 오류를 발생시킨다. 본 논문에서는 채널 시변의 원인을 주파수 옵셋과 도플러효과로 규정하고, 주파수 옵셋을 보정하기 위해 기존의 선형보간법(LI: linear interpolation method)대신 선형위상보간법(LPI: linear phase interpolation)과 도플러효과에 의한 ICI를 제거하기 위해 기존의 주파수영역 둥화기법보다 효과적인 시간영역 등화기법을 제안한다. 제안된 기법이 주파수 옵셋이 있는 시변다중경로 페이딩 환경에서 OFDM 시스템에 적합함을 컴퓨터 모의실험을 통해 확인한다.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.12 no.2
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• pp.234-244
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• 2001

다양한 지형정보를 제공하는 SAR 인터페로메트리 기법은 레이다의 위상정보를 이용하여 정밀 고도정보를 추출하는 첨단기술이다. SAR 데이터 주파수 aliasing 현상은 도플러 중심 주파수가 중심에 위치하지 않으므로 발생된느 것으로 주요 잡음요인으로 작용된다. 따라서 본 논문에서는 SAR 인터페로메드리 전체 프로세싱 과정의 주요 모듈중 하나인 주파수 aliasing 제거 모듈의 구현 방안을 연구하였다. 본 논문에서 사용된 aliasing 제거 기법은 랩어라운드교정기법으로서 실험결과 매우 효과적으로 작용하였음을 알 수 있었으며, 제안된 구현방안은 차후 실제 적용이 가능함을 제시하였다.

• Proceedings of the Korea Water Resources Association Conference
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• 2015.05a
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• pp.517-517
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• 2015

레이더에 수신된 신호는 신호처리기를 통해 자료의 해석시 불필요한 지형에코를 제거하는 과정을 거친다. 신호처리기의 필터는 레이더의 기종에 따라 다르나, 일반적으로 도플러 속도나 스펙트럼 폭의 값에 따라 지형에코를 제거하며, 이 값들에 따라 번호를 부여하여 필터를 선택적으로 이용할 수 있도록 되어 있다. 본 연구에서는 국토교통부에서 운영하고 있는 비슬산 강우레이더와 소백산 강우레이더의 필터번호에 따른 반사도의 빈도 영역 그래프, 반사도-차등반사도의 빈도 산포도, 반사도와 차등반사도의 평균 및 표준편차를 통해 적정 필터를 선정하고자 하였다. 이 때, 지형에코와 기상에코의 제거 정도 확인을 위해 레이더 관측반경 50 km를 기준으로 비교를 수행하였다. 그 결과, 1번 필터 이후에는 필터에 따른 큰 변화가 없어 1번 필터를 사용하는 것이 기상에코를 보존하면서 지형에코를 제거하는 효과가 가장 좋은 것으로 판단되었다.

• Journal of Convergence for Information Technology
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• v.10 no.9
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• pp.15-21
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• 2020

This paper presents the outlier detection algorithm in the estimation method of a source location and velocity based on two-step weighted least-squares method using time difference of arrival(TDOA) and frequency difference of arrival(FDOA) data. Since the accuracy of the estimated location and velocity of a moving source can be reduced by the outliers of TDOA and FDOA data, it is important to detect and remove the outliers. In this paper, the method to find the minimum inlier data and the method to determine whether TDOA and FDOA data are included in inliers or outliers are presented. The results of numerical simulations show that the accuracy of the estimated location and velocity is improved by removing the outliers of TDOA and FDOA data.

• The Journal of the Acoustical Society of Korea
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• v.36 no.4
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• pp.273-278
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• 2017

In this paper, a post-processing algorithm to suppress reverberation for continuous-wave active sonar system is developed. The developed algorithm is designed for a low-doppler environment where the target echo is not distinguishable from the reverberation. The algorithm is developed based on overlapping nonnegative matrix factorization method. The algorithm analyzes the frequency characteristics of transmitting ping signal, then suppresses the reverberation using time-frequency characteristics of the received signal. Simulations performed in order to evaluate the proposed algorithm, and the results show that the proposed algorithm makes 6 dB signal-to-reverberation ratio enhancement in various reverberation energy conditions.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.46 no.6
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• pp.78-85
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• 2009

In time-varying multipath fading channels, orthogonal frequency division multiple access (OFDMA) uplink systems suffer severe performance degradation caused by inter-channel interference (ICI). In this paper, we propose a hybrid interference cancellation (HIC) for suppressing the degradation effect of ICI. The proposed HIC can achieve both exact interference cancellation and low detection complexity through efficient combination of parallel detection and serial cancellation. Simulation results show that, as the effect of Doppler increases, the proposed HIC achieves bit error rate (BER) performance enhancement in compared with severe performance degradation of conventional OFDMA receivers. In addition, both the computational complexity and total detection time are reduced.