• 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.

• Proceedings of the KIPE Conference
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• 2014.07a
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• pp.451-452
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• 2014

본 논문에서는 단상 계통연계형 컨버터의 전원 위상각을 추종함에 있어 필수적인 전압 센서의 옵셋 오차에 대한 영향을 분석하고 이를 검출 및 보상하기 위한 알고리즘을 제안하였다. 전원전압 측정에 따른 옵셋 오차는 전원 주파수의 1배 맥동을 야기하여 전원 위상각이 왜곡된다. 왜곡된 전원 위상각에 의한 좌표변환시 동기 좌표계 dq축 전류에 전원 주파수 1배의 맥동을 야기하며 이는 계통측 상전류에 직류성분과 전원 주파수 2배의 고조파 성분을 발생시키게 된다. 따라서, 본 논문에서는 전원측정시 야기되는 옵셋 오차의 영향을 분석하고 이의 검출신호로 전원 위상각 제어기의 적분출력을 선정하였다. 또한 RMS(Root Mean Square) 기법을 이용하여 옵셋 성분을 검출 및 보상하는 알고리즘을 제안하였다. 제안된 알고리즘의 성능은 시뮬레이션과 실험을 통하여 검증하였다.

• Korean Journal of Remote Sensing
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• v.31 no.2
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• pp.101-110
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• 2015

Synthetic Aperture Radar Interferometry (InSAR) is affected by various noise source such as atmospheric artifact, orbital error, processing noise etc.. Especially, one of the dominant noise source for long-wave SAR system, such as ALOS PALSAR (L-band SAR satellite) is the ionosphere effect because phase delays on radar pulse through the ionosphere are proportional to the radar wavelength. To avoid misinterpret of phase signal in the interferogram, it is necessary to detect and correct ionospheric errors. Recently, a MAI (Multipler Aperture SAR Interferometry) based ionospheric correction method has been proposed and considered one of the effective method to reduce phase errors by ionospheric effect. In this paper, we introduce the MAI-based method for ionospheric correction. Moreover we propose an efficient method that apply the method over non-coherent area using directional filter. Finally, we apply the proposed method to the ALOS PALSAR pairs, which include the west sea coast region in Korea. A polynomial fitting method, which is frequently adopted in InSAR processing, has been applied for the mitigation of phase distortion by the orbital error. However, the interferogram still has low frequency of Sin pattern along the azimuth direction. In contrast, after we applied the proposed method for ionospheric correction, the low frequency pattern is mitigated and the profile results has stable phase variation values within ${\pm}1rad$. Our results show that this method provides a promising way to correct orbital and ionospheric artifact and would be important technique to improve the accuracy and the availability for L-band or P-band systems.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2010.11a
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• pp.1-3
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• 2010

본 논문에서는 VSB 수신기를 위한 반송파 위상 오차에 독립적인 심벌 타이밍 옵셋 추정 알고리즘을 제안하고자 한다. 심벌 타이밍 옵셋 추정에 대표적인 알고리즘인 가드너 방법은 반송파 위상 옵셋이 포함된 VSB 수신기에서는 타이밍 옵셋을 추정할 수 없다. 본 논문에서는 수신신호의 공액 곱 연산을 통하여 신호의 스펙트럼을 확장하고 반송파 위상 옵셋을 상쇄 하였고, 그 후 가드너 알고리즘을 통하여 인접 스펙트럼 간의 중복부분을 발생시켜, 타이밍 옵셋을 추정하는 방식을 연구하였다. 시뮬레이션 결과, 제안하는 알고리즘은 VSB 수신기에서 반송파 위상 오차에 영향을 받지 않고, 정확하게 타이밍 옵셋을 추정할 수 있는 것으로 나타났다.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.41 no.3
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• pp.25-32
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• 2004

An advanced algorithm for measurement of phase angle between two sinusoidal signals is proposed in this paper. This algorithm uses discrete sample data of two input signals for calculation of phase angle and amplitude. And the key parameters of the measurement algorithm are described by analytical express, so the calculation of phase angle is simplified. In this paper it is proved that harmonic distortion of the input sinusoidal signals does not affect the measurement value of phase angle by using the proposed algorithm when a whole cycle is sampled. And measurement error by the white Gaussian noise is very small compared by other algorithms.

• Journal of the Korea Convergence Society
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• v.6 no.5
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• pp.249-255
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• 2015

In this paper, we present an azimuth error analysis for the correlative interferometer direction finding. The correlative interferometer is a direction finding method that compares the theoretical and measured phase differences. The direction of the radio transmitter can be estimated by obtaining the maximum correlation between two data sets. We used a 5-element circular array antennas arranged in a circle. To derive the correlation function between antenna elements, we assume that the incident plane wave arrives from a certain angle and the phase difference of each antenna can be derived by comparing with the reference. The suggested direction finding gives a relatively accurate result even if the radio transmitter is located in the higher altitude.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.14 no.1
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• pp.7-13
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• 2021

This paper proposes a method to minimize the target's direction detection error using RADAR. The radar system cannot accurately detect the target direction due to the phase error of he received signal. The proposed method of this study obtains a phase by applying an root mean square to each antenna incident signal, and reduces the phase error by using an optimal signal to noise ratio. In the simulation result, the probability of detecting the target direction is the best when the antenna spacing is half wavelength. The conventional method of direction detection probability 10-1.7 and the proposed method is 10-3.3. The target detection direction of the existing method represents [-8°,8°] with an error of 2 degrees. The target detection direction of the proposed method is shown in [-10°,10°], and all target directions are accurately detected. In the future, There is need for a method to reduce the phase error even though the resolution decrease.

• Korean Journal of Optics and Photonics
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• v.22 no.5
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• pp.207-213
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• 2011

We propose a new method to measure the phase errors of an AWG(arrayed waveguide grating) through Monte-Carlo analysis. In the frequency domain method, we used the Monte-Carlo method to fit the theory to the experimental results. The phase and amplitude values are obtained from the fitted theory. To verify our method, we carried out a simulation. Some phase errors were included to make a virtual interferogram and we measured the actual AWG phase errors from it by our method. The results show that our method gives good results if the laser tuning range is larger than 1.7 times of the AWG FSR(free spectral range) and if the phase errors are within ${\pm}50^{\circ}$.

• Proceedings of the Korean Institute of Communication Sciences Conference
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• 1987.04a
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• pp.206-211
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• 1987

본 논문에서는 입력 신호인 정현파의 위상을 PGZC(positive going zero corssing)에 대해 한주기당 2회씩 추적하도록 하는 디지털 위상도기 회로(DPLL)을 제시한다. 제시된 루루프는 한 주기당 2번의 표본화를 갖도록 함으로써 한 주기당 하나의 표본을 취하는 기존의 DPLLqhek 정상 상태에서의 위상오차 변동범위가 전체적으로 1/2로 감소되었고, 연속 표본들간의 오차와 양자화 준위의 선택에 따라서 루우프의 천이 응답이 좋아짐을 알 수 있었다. 그 해석적 결과를 실제적으로 요구되는 조건류에 대하여 컴퓨터 시뮬레이션을 행함으로써 검증하였다.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.29 no.11
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• pp.828-833
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• 2018

It is well known that reflected waves and resonance affect phase distortion. In addition, phase delay can be distorted by antenna impedance. In this study, we analyze the phase delay variation caused by the antenna impedance, considering mutual coupling effects. In addition, we confirm the beam steering characteristics. When was -10 dB and -7 dB, the maximum phase delay error was $18.5^{\circ}$ and $26.5^{\circ}$, respectively. The Monte Carlo simulation with an eight-element linear array antenna demonstrated that the RMS error of the beam steering angle ranged from $0.19^{\circ}$ to $0.4^{\circ}$, and the standard deviation ranged from $0.14^{\circ}$ to $0.33^{\circ}$ when the beam steering angle was in the range of $0^{\circ}$ to $30^{\circ}$, with the uniformly distributed phase error of $18.5^{\circ}$ and $26.5^{\circ}$. The side lobe level increased from 0.74 dB to 1.21 dB by the phase error from the theoretical value of -12.8 dB, with a standard deviation of 0.31 dB to 0.51 dB. This is verified by designing an eight-element spiral array antenna.