• 한국전자파학회논문지
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• 제21권10호
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• pp.1121-1127
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• 2010

본 논문에서는 X-대역 Radant lens 4-bit 위상 변위기 설계에 필요한 $11.25^{\circ}$, $22.5^{\circ}$, $45^{\circ}$ 위상 변위 레이어(layer) 중에서 $45^{\circ}$ 레이어의 등가회로에 관하여 기술한다. $45^{\circ}$ 위상 변위 레이어에 대한 CST사의 MWS (Microwave Studio)와 Agilent사의 ADS(Advanced Design System) 시뮬레이션을 비교 분석하여 등가회로를 추출하고, 등가회로를 통해 얻을 수 있는 이론치와 측정치를 비교한다. 또한, 추출된 등가회로를 활용하여, 4-bit Radant lens의 위상 bit 시뮬레이션 결과도 제시한다.

• Journal of Power Electronics
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• 제10권2호
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• pp.132-137
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• 2010

Interleaving techniques are widely used to reduce input/output ripples and to increase the power capacity of boost converters operating in critical conduction mode. Two types of phase-shift control schemes are studied in this paper, the turn-on time shifting method and the turn-off time shifting method. It is found that although the turn-off time shifting method exhibits better performance, it suffers from sub-harmonic oscillations at high input voltages. To solve this problem, an intensive quantitative analysis of the sub-harmonic oscillation phenomenon is made in this paper. Based upon that, a novel modified turn off time shifting control scheme for interleaved boost converters operating in critical conduction mode is proposed. An important advantage of this scheme is that both the master phase and the slave phase can operate stably in critical conduction mode without any oscillations in the full input voltage range. This method is implemented with a FPGA based digital PWM control platform, and tests were carried out on a two-phase interleaved boost PFC converter prototype. Experimental results demonstrated the feasibility and performance of the proposed phase-shift control scheme.

• 한국광학회지
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• 제14권2호
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• pp.184-188
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• 2003

TM 모드에는 영향을 끼치지 않으면서 TE 모드의 위상만을 변조시키는 P-I-i-I-N $GaAs/Al_{0.35}Ga_{0.65}As$ 도파로 위상변조기를 제작하였다. TE 모드에 대해서만 위상변조를 일으키게 하기 위해 P-I-i-I-N 구조를 선택하였다. Fabry-Perot 공명 방법을 이용해서 TE-와 TM 모드에 대해 $\lambda=1.55$\mu\textrm{m}$ 파종에서 각각 측정하였다. TE-편광된 빛에 대한 위상변조 효율은 $\Delta\phi=7.9^{\circ}/V.mm$ 였다. 이것은 비슷한 구조를 갖는 위상변조기의 변조 효율 보다 거의 2.5배정도 향상된 결과이다. 또한, TM-편광된 빛에 대해 서는 위상변조가 관측되지 않았다.

• 한국통신학회논문지
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• 제29권3A호
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• pp.311-317
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• 2004

Varactor 다이오드와 branch coupler를 이용한 반사형 아날로그 위상 변위기 설계에 대하여 기술하였다. 1단의 위상 변위기로 위상 변위를 크게 하기 위하여 마이크로 스트립 stub기법을 사용하였으며 2.260GHz 주파수대에서 제작 결과 170$^{\circ}$의 위상이 변화함을 확인하였다. 측정된 삽입손실을 3㏈ 이하이었고. 반사 손실은 12㏈ 이상이었다. 본 논문에서는 설계 기법과 제자 및 실험 결과를 상세히 기술하였다.

• Journal of the Optical Society of Korea
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• 제2권2호
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• pp.74-79
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• 1998

The use of a fiber Fabry-Perot interferometer (FFPI) as an optical current transducer is demonstrated. A conventional inductive pickup coil converts the time-varying current I(t) being measured to a voltage waveform V(t) applied across a piezeolectric strip to which the FFPI is bonded. The strip experiences a longitudinal expansion and contraction, resulting in an optical phase shift ${\phi}(t)$ in the fiber proportional to V(t). This phase shift is measured using a frequency-modulated semiconductor light source, photodiodes to monitor the reflected light from the FFPI and the laser power, and a digital signal processor. Calibration routines compute V(t) and I(t) from the measured phase shift at a l KHz rate. Response to 60 Hz ac over the design range 0-1300A rms is characterized Transient response of the FFPI transducer is also measured.

• ETRI Journal
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• 제35권1호
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• pp.150-153
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• 2013

In this letter, a compact and fully printed composite right- and left-handed (CRLH) dual-band power divider is proposed. The branches of the conventional Wilkinson power divider are replaced by subwavelength CRLH phase-shift lines having $+90^{\circ}$ for one frequency and $-90^{\circ}$ for another frequency for dual-band and miniaturization performance. Equations are derived for the even- and odd-mode analysis combined with the dual-band CRLH circuit. A PCS and a WLAN band are chosen as the test case and the circuit approach agrees with the CAD simulation and the measurement. Additionally, the CRLH property is shown with the dispersion diagram and the eightfold size reduction is noted.

• Journal of Power Electronics
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• 제15권5호
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• pp.1158-1167
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• 2015

In this paper, a new hybrid DC-DC converter is proposed for electric vehicle 3.3 kW on-board battery charger applications, which can be modulated in a phase-shift manner under a fixed frequency or frequency variation. By integrating a half-bridge (HB) LLC series resonant converter (SRC) into the conventional phase-shift full-bridge (PSFB) converter with a full-bridge rectifier, the proposed converter has many advantages such as a full soft-switching range without duty-cycle loss, zero-current-switching operation of the rectifier diodes, minimized circulating current, reduced filter inductor size, and better utilization of transformers than other hybrid dc-dc converters. The feasibility of the proposed converter has been verified by experimental results under an output voltage range of 250-420V dc at 3.3 kW.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2011년도 제42회 하계학술대회
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• pp.1784-1785
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• 2011

PS(Phase Shift) 방식을 이용하여 3차원 이미지 형상복원 시스템을 구현하였다. PS 방식은 위상을 이동시켜서 얻어진 강도를 arctan 시킴으로써 $-{\pi}{\sim}{\pi}$ 범위의 접혀진(wrapped) 위상을 얻을 수 있으며, 이러한 wrapped 위상을 위상 펼침(unwrapping) 알고리즘을 이용하여 불연속을 제거할 수 있다. 얻어진 위상 정보는 물체의 높이 정보에 비례하기 때문에 위상 분포로써 3차원 형상을 복원할 수 있다. Unwrapping 알고리즘에는 다양한 방식이 있지만 본 연구에서는 LabVIEW 프로그램을 이용하여 Goldstein 알고리즘을 구현하였으며, 감마(Gamma) 효과에 의한 노이즈를 줄이기 위하여 프로젝트와 카메라의 보정(calibration) 프로그램을 개발 및 적용하였다. 이와 같은 실험을 통하여 효과적으로 3차원 형상 정보를 얻을 수 있었다.

• 전기학회논문지
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• 제58권4호
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• pp.795-800
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• 2009

Surface plasmon resonance (SPR) has been widely used for biological and chemical sensing applications. The present study investigates numerically the optical characteristics for the single Au film and bimetallic Ag/Au film SPR configurations by using the multiple beam interference matrix (MBIM) method. We use the prism coupling method, especially Kretschmann configuration for excitation of surface plasmon wave (SPW). The estimated results of reflectance, phase shift and magnetic field intensity enhancement factor are provided for finding out the optimum configuration with high sensitivity for SPR measurement. As a result, the optimum thicknesses are found to be 52 nm for a single Au film and 5 nm to 36 nm for bimetallic Ag-Au film. From the comparison of full width half maximum (FWHM) values for reflectance, phase shift, and enhancement of magnetic field intensity, it is concluded that the highest sensitivity can be obtained when using the phase shift for SPR sensor.

• Journal of information and communication convergence engineering
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• 제14권2호
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• pp.78-83
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• 2016

In underwater acoustic communication, the transmitted signals are severely influenced by the reflections from both the sea surface and the sea bottom. As very large reflection signals from these boundaries cause an inter-symbol interference (ISI) effect, the communication quality worsens. A channel estimation-based equalizer is usually adopted to compensate for the reflected signals under the acoustic communication channel. In this study, a feed-forward equalizer (FFE) with the least mean squares (LMS) algorithm was applied to a quadrature phase-shift keying (QPSK) transmission system. Two different types of equalizers were adopted in the QPSK system, namely a real-coefficient equalizer and a complex-coefficient equalizer. The performance of the complex-coefficient equalizer was better than that of two real-coefficient equalizers. Therefore, a Hilbert transform was applied to the real-coefficient binary phase-shift keying (BPSK) system to obtain a complex-coefficient BPSK system. Consequently, we obtained better results than those of a real-coefficient equalizer.