• Journal of KSNVE
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• v.5 no.4
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• pp.453-460
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• 1995

본 논문에서는 정현파 소음을 제어하기 위한 filtered-x LMS에 바탕을 둔 새로운 적응 알고리듬을 제안하였다. 이러한 알고리듬은 두개의 연속적인 계수조정 식으로, 제어기의 계수를 조정한다. 서로 독립인 각 주파수별로 처리하기 때문에 빠른 수렴을 얻을 수 있다. 두번째식은 이차경로로 인한 위상지연을 추정한다. 정현 파 신호 주파수보다 4배 이상 빠른 표본화 주파수를 선택하여 추정된 위상지연 추정 값은 $2{\pi}f_0$만큼 오차를 나타내며, 이 값은 $\pi$2보다 작다. 정현파 신호의 주파수를 알면 이러한 오차는 $2{\pi}f_0$를 더함으로써 제거할 수 있다. 이러한 방법은 위상지연이 $\pi$2보다 큰 경우 수렴속도를 증가시킨다는 사실을 실험을 통하 여 알 수 있다. 추정된 위상지연은 제어기 계수값을 조정하는데 필요한 필터링된 참조신호를 발생시키믄데 사용된다. 참조신호의 위상지연이 각 주파수 성분별로 수행 되기 때문에, 콘볼루션 연산이 생략되어 계산량을 줄일 수 있다. 또한 연속적으로 위상지연을 추정하기 때문에 시변 상황에 적용이 가능하다. 조정식의 수렴조건을 유도하였다. 제안된 알고리듬은 제어기 계수를 추정하는데 바이어스가 없으며, 위상 지연추정을 위한 수렴상수의 최대허용치는 제어기계수에 대한 수렴상수에 반비례함을 이론적으로 분석을 통해 알 수 있다. 모의실험을 통하여 제안된 알고리듬이 filtered-x LMS 알고리듬에 바탕을 둔 다른 알고리듬보다 환경변화에 우수한 성능을 보임을 알 수 있다.

• Korean Journal of Optics and Photonics
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• v.25 no.3
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• pp.150-154
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• 2014

The conditions under which a composite retarder consisting of two different retardation plates can be operated as a tunable quarter-wave plate are derived. The explicit expressions for the azimuthal angle of a linear polarizer and those of two retardation plates to generate circularly polarized light are presented as a function of retardation angles. Those expressions for the azimuthal angles derived using the Jones matrix formalism are verified as identical to the expressions derived from the analysis of the trajectory on a Poincar$\acute{e}$ sphere. A couple of examples are presented for generating circularly polarized light when two identical retardation plates are used.

• Proceedings of the Korea Information Processing Society Conference
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• 2024.05a
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• pp.459-460
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• 2024

본 연구에서는 노이즈가 있는 신호에서 코릴레이션과 위상자를 이용해 특정 주파수 성분의 세기와 위상을 검출하고 시간 지연이 있는 두 개의 신호에서 위상차를 통해 시간 지연을 추정하는 알고리즘을 제시하였으며 마이크로폰 어레이와 증폭 회로를 구성하여 단일 주파수 음원의 시간 지연 추정을 구현하였다. 이는 단일 주파수 신호의 시간 지연을 검출하는데 있어 기존의 방식들에 비해 단순하며 보다 자원이 한정적인 임베디드 시스템에서 사용될 수 있을 것으로 예상된다.

• Journal of the Microelectronics and Packaging Society
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• v.29 no.4
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• pp.29-34
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• 2022

A fabrication process of smart windows with controllable visible light transmittance by using retardation films is proposed. The 𝛌/4-phase retardation films that can convert a linearly polarized light into circularly polarized light are achieved through photo-alignment layers and reactive mesogen (RM) coating process. Two sheets of the fabricated retardation films with different orientation angles induced to light transmission mode (45°/-45°) and light blocking mode (45°/45°) for visible wavelength. We evaluated retardation characteristics according to the thickness of the birefringent RM material and found out the optimal condition for the film with 𝚫n·d of 𝛌/4-phase. The proposed structure of the smart window exhibited the light blocking ratio improved by more than 20% in the visible wavelength (380 nm to 780 nm). Finally, it was confirmed that the feasibility of the window structure by applying to a prototype for a smart window with a size of 150 × 150 mm².

• Journal of the Korea Institute of Information and Communication Engineering
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• v.13 no.11
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• pp.2378-2384
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• 2009

A novel phase-locked loop(PLL) architecture of sub-micron locking time has been proposed. Input frequency is multiplied by using a delay-locked loop(DLL). The input frequency of a PLL is multiplied while the PLL is out of lock. The multiplied input frequency makes the PLL having a wider loop bandwidth. It has been simulated with a $0.18{\mu}m$ 1.8V CMOS process. The simulated locking time is $0.9{\mu}s$ at 162.5MHz and 2.6GHz, input and output frequency, respectively.

• Korean Journal of Optics and Photonics
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• v.13 no.3
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• pp.240-244
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• 2002

We proposed a novel temperature sensor based on the phenomena that the phase difference between principal polarization states in an optical retarder is a function of temperature. The polarization state of an optical beam is changed as it passes through the optical retarder, with the change dependent on the temperature. The temperature of the optical retarder is determined by comparison of the power difference between principal polarization states. A temperature sensor was successfully implemented using a polarization maintaining fiber of length 100 mm as the optical retarder. The change rate of phase difference on temperature was 0.236$^{\circ}C$$_{-1}$ and the measurement error was $\pm$0.038$^{\circ}C$ over the temperature region of -2.6$^{\circ}C$~3.4$^{\circ}C$.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.32 no.4
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• pp.34-42
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• 2004

In this paper, a double gimbal is used for roll/yaw attitude control of spacecraft and two feedback controllers are designed. One is a PD controller of no phase difference between roll and yaw control input. The other is a PD controller with a phase lag compensator about the yaw control input. The phase lag compensator is designed a first order system and a lag parameter is designed for the control of yaw angle. There are two case simulations for each of controllers; constant disturbance torques and initial errors of nutation. We obtain the results through simulations that a steady-state error and a rising time of yaw angle are developed by the compensator. In this paper, simulation parameters use the values of KOREASAT 1.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37A no.10
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• pp.895-902
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• 2012

In this paper, we propose a novel equalizer to compensate for the group delay including AM/PM nonlinear distortion characteristics by the nonlinear power amplifier (PA). The group delay characteristic is a nonlinear non-constant time delay that appears differently depending on each frequency component. The phase distortion by AM/PM characteristics arising from the power amplifier is a major factor to increase group delay. By the group delay distortion, the signal in the constellation expands and is rotated. Considering the problem mentioned above, the nonlinear time delay that appears differently depending on each frequency component is classified as a static group delay and AM/PM characteristic of PA, the different phase transitions depending on the size of input signal as a dynamic group delay. Static group delay estimates and compensate for phase distortions in the frequency domain with type-based method and dynamic group delay compensates for phase rotation in the time domain. We confirmed that the group delay compensation techniques were enough to compensate the group delay characteristics including AM/PM characteristics of the power amplifier.

• Applied Chemistry for Engineering
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• v.17 no.4
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• pp.381-385
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• 2006

We applied a new analyzing technique for the polyurethane acrylate hybrid emulsion sample composed of polyurethane resin and acrylate resin using the phase-lag mapping techniques of atomic force microscopy. For the analysis, we synthesized similarly sized pure polyurethane dispersion and acrylate emulsion particles, which were used for measuring the standard phase-lag intensities for each material. Based on these signal intensity, we could discriminate acryl particle in the polyurethane dispersion matrix with the resolution of a few tens of nanometers. Thus, the techniques show a new possibility in the analysis of the organic two-phase particles, and we believe the techniques are helpful to design organic particles.

• The Transactions of the Korean Institute of Power Electronics
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• v.6 no.2
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• pp.180-190
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• 2001

In this paper, a method of reducing torque ripples caused by phase winding inductances in BLDCM(Brushless DC Motor) drives is presented. In order to compensate the inductive current delays, commutation angle is controlled by the value compensating angle varied in accordance with rotational speed. Using the microprocessor AVR 8515, the proposed compensator is implemented and experiments are done with a 4-pole 3-phase BLDCM. The results show the remarkable reduction of torque ripple at whole speed ranges.