• Journal of the Korea Convergence Society
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• v.10 no.1
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• pp.1-6
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• 2019

In this paper, we have studied a direction finding method of the radio signal by comparing the phase difference and its pattern from the uniform circular array antenna. In the phase comparison direction finding, if the length of the antenna baseline is longer than 0.5 wavelength of the incident signal, azimuth ambiguity occurs in which two or more azimuth angles are calculated in the same phase difference. The azimuthal ambiguity is removed by fusing the phase difference of the 5 antennas. The developed ambiguity elimination technology reduces the azimuth error where the antenna baseline is shorter than 1.236 wavelength in the uniform circular array with five antennas. This algorithm is very useful for the design of direction finder of an electronic information system.

• Proceedings of the Korean Institute of Intelligent Systems Conference
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• 2006.11a
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• pp.388-390
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• 2006

본 논문은 종합주가지수, 코스닥 지수의 시계열 일간 데이터의 위상분석을 통해 시계열간의 연관성을 분석하였다. 시계열의 데이터는 비선형, 비정상이다. 따라서 위상성분의 정확한 추출을 위해서 전통적인 수학적 방법이 아닌 순간 위상값을 이용한 새로운 신호분석 방법을 사용하여 두 시계열의 연도별 위상차의 왜도와 첨도값을 기준으로 시계열의 상관특성을 살펴보았다.

• Journal of the Korean Society for Nondestructive Testing
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• v.31 no.2
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• pp.157-164
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• 2011

This work is devoted to the technique application of lock-in infrared Thermography in the shipbuilding and ocean engineering industry. For this purpose, an exploratory study to find the optimized test conditions is carried out by the design of experiments. It has been confirmed to be useful method that the phase contrast images were quantified by a reference image and weighted by defect hole size. Illuminated optical intensity of lower or medium strength give a good result for getting a phase contrast image. In order to get a good phase contrast image, lock-in frequency factors should be high in proportion to the illuminated optical intensity. The integration time of infrared camera should have been inversely proportional to the optical intensity. The other hand, the difference of specimen materials gave a slightly biased results not being discriminative reasoning.

• Korean Journal of Optics and Photonics
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• v.23 no.4
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• pp.135-142
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• 2012

We have developed a measurement method of the refractive index profile of an optical fiber by using diffraction phase microscopy. In the microscope system, the reference light was extracted directly from the probe light that passed through the sample by means of pinhole filtering with a diffraction grating. The spatial interference pattern produced by the probe light and the reference light was processed to generate the phase image of the sample fiber. The index profile was obtained by the inverse Abel transform of the phase profile. In order to remove the background phase that originated from the index difference between the cladding and the surrounding medium, the background phase was calculated from the phase data of the cladding to make a core phase profile that can be directly transformed to the index profile of the core without the full phase image that includes the entire cladding part.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.14 no.8
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• pp.777-786
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• 2003

The phase noise characteristics of the phase-locked loop frequency synthesizer were predicted based on the analysis for phase noise contribution of noise sources. The proposed phase noise model in this paper more accurately predicts the phase noise spectrum of frequency synthesizer. To accurately model the phase noise contribution of noise sources in frequency synthesizer, the phase noise sources were analyzed via modeling of the frequency divider and phase noise components using Leeson model for reference signal source and VCO. The phase noise transfer functions to VCO from noise sources were analyzed by superposition theory and linear operation of phase-locked loop. To evaluate the phase noise prediction model, the frequency synthesizers were fabricated and were evaluated by measured data and prediction data.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.27 no.2C
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• pp.191-200
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• 2002

A frequency synthesizer that can be used in IMT-2000 was designed and fabricated using dual loop PLL(Phase Locked Loop) in this paper. For improving phase noise characteristic two loops, reference loop and main loop, were divided. Phase noise was improved by transformed clamp type voltage controled oscillator and optimizing loop bandwidth in reference loop. And voltage controlled oscillator open loop gain in main loop. Fabricated the frequency synthesizer had 1.81GHz center frequency, 160MHz tuning range, 13.5dBm output power and -119.73dBc/Hz low phase noise characteristic.

• The Proceedings of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.11 no.3
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• pp.106-113
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• 1997

In uninterruptible power supply(UPS), a high speed phase control is usually required to compensate transients in the output voltage at the instant of transfer from the ac line to the inverter when the ac line fails or backs to the ac line in case of the inverter fails. To overcome this problem, this paper pre¬sents the closed digital phase-locked loop(DPLL) techniques designed by full software with TMS320C31 digital signal processor and describes the functional operation of the proposed DPLL. Fi¬nally, the performance of the proposed DPLL is shown and discussed through simulation and experiment.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.19 no.5
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• pp.971-980
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• 1994

The need increased capacity in the cellular system has resulted in the adoption of digital technology with CDMA as the channel access method. It has been recognized that the distinction of the base station is important for its performance in CDMA, since the same spreading sequences are used by the all base stations. Time offset of the pseudo-random noise binary code are used to distinguish signals received at a mobile station from different base station. But the start of the zero offset PN sequence is chosen arbitrary without the background of the systematic and mathematical elaboration. This paper proposes a mothed that define the start of the zero offset PN sequence mathematically. This paper also discusses a method that can easily calculate the time offset of the received spreading sequence with respect to the zero offset PN sequence.

• Proceedings of the IEEK Conference
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• 2001.06a
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• pp.197-200
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• 2001

본 논문에서는 병렬귀환 유전체 발진기를 P-HEMT 게이트단의 바이어스 진압을 제어시켜 안정된 위상동기신호가 나타나도록 P-HEMT 게이트 바이어스 튜닝에 의한 Ku-band 고안정 위상동기 마이크로파 발진기를 설계하였다. 위상동기방식은 외부에서 제공되는 125MHz의 기준주파수를 SRD로 체배시켜 하모닉 신호를 이용한 마이크로파 샘플링 위상검파 방식으로 설계하였으며, 고안정 특성과 저위상잡음을 나타내는 위상동기 마이크로파 발진기(phase locked microwave oscillator)를 바랙터 다이오드를 사용하지 않고 P-HEMT의 게이트단을 동조시키는 방식으로 위상동기 발진기를 설계하고 게이트 바이어스에 따른 위상잡음 관계를 분석하였다

• Information and Communications Magazine
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• v.10 no.5
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• pp.53-70
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• 1993

위상 복원 문제는 어떤 신호의 푸리에 변환의 크기로부터 푸리에 위상, 또는 그 신호 자체를 구하는 문제로서 신호처리, 천문학, X-선 결정학, 전자현미경학, 광학, synthetic aperture radar 등과 같은 많은 물리학의 분야에서 일어난다. 일반적으로, 이 위상 복원 문제는 유일한 해를 갖지 않기 때문에, 이 문제를 풀기 위하여 사전 정보로 주어지는 원하는 신호의 성질을 제한조건으로 주어 이 문제가 유일한 해를 갖도록 한 뒤 이 원하는 신호를 구하는 방법을 사용해왔다. 이 논문에서는 위상 복원 문제를 소개하고, 이 문제의 중요성, 기본 이론 등을 알아보고, 지금까지 제안이 되었던 방법들을 분야별로 묶어 신호처리의 관점에서 소개한다. 먼저 수학적인 기초에 대하여 소개하고, 푸리에 변환의 크기를 보존하는 변환들에 대하여 알아본 뒤, 위상 복원 문제를 풀기 위하여 제안이 되었던 방법들을 1)하나의 푸리에 변환의 크기가 주어졌을 때의 위상 복원, 2)더해지는 기준 신호가 있을 때의 위상 복원, 3)곱해지는 신호(윈도우)를 이용한 위상 복원으로 나누어 소개한다.