• 대한산업공학회지
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• 제22권2호
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• pp.165-177
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• 1996

This paper presents a navigation method for a mobile robot which can follow a path drawn on a monitor screen. The current position and heading direction of the mobile robot are obtained using a single camera from a single image of the guide mark projected on a convex mirror. This proposed method eliminates the need to rotate or tilt the camera to track the guide mark, because the convex mirror and a stationary camera provide a panoramic view of the surrounding area. As guide marks, fluorescent lamps on the ceiling, door frames, or any other natural line segment can be used without adding any artificial elements to them.

• Journal of the Optical Society of Korea
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• 제12권3호
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• pp.157-161
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• 2008

A wavelength-selective reflector, composed of a double-ring-resonator add/drop filter and a loop-back mirror at the drop port to be used for a hybrid-integrated tunable laser is designed and fabricated. High-index-contrast polymer waveguide is used to realize a compact device as small as $2mm{\times}0.4mm$. The radii of the rings are slightly different from each other to obtain a wide wavelength tuning via a vernier effect. Peak reflectivity is measured to be 52% for TE mode and polarization-dependent wavelength shift is 0.95 nm. The tuning range is measured to be about 42 nm for applied current as small as 46 mA.

• Current Optics and Photonics
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• 제5권3호
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• pp.261-269
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• 2021

Binary-phase complex spatial light modulators (BP-C-SLMs) are proposed and simulated. This study shows that bottom-top mirror-symmetrical uniaxial systems between two orthogonal polarizers allow one to construct BP-C-SLMs. BP-C-SLMs double the information-handling capacity per pixel, compared to the conventional amplitude-only spatial light modulators (A-SLMs), as well as being simply implemented with a single spatial light modulator (SLM), rather than a combination of an A-SLM and a binary-phase SLMs. Under limited conditions, BP-C-SLMs can control only the amplitude in single-phase space, and act as A-SLMs.

• Current Optics and Photonics
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• 제7권6호
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• pp.708-713
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• 2023

A robust all-fiber nonlinear amplifying loop-mirror-based mode-locked femtosecond laser is demonstrated. Power-dependent nonlinear phase shift in a Sagnac loop enables stable and power-efficient mode-locking working as an artificial saturable absorber. The pump power is adjusted to achieve the lowest intensity noise for stable long-term operation. The minimum pump power for mode-locking is 180 mW, and the optimal pump power is 300 mW. The lowest integrated root-mean-square relative intensity noise of a free-running mode-locked laser is 0.009% [integration bandwidth: 1 Hz-10 MHz]. The long-term repetition-rate instability of a free-running mode-locked laser is 10^-7 over 1,000 s averaging time. The repetition-rate phase noise scaled at 10-GHz carrier is -122 dBc/Hz at 10 kHz Fourier frequency. The demonstrated method can be applied as a seed source in high-precision real-time mid-infrared molecular spectroscopy.

• 한국전자파학회논문지
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• 제27권2호
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• pp.212-215
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• 2016

본 논문에서는 $0.18{\mu}m$ CMOS 공정을 사용하여 5.08 GHz에서 동작하는 링 전압 제어 발진기(Ring Voltage Controlled Oscillator, Ring VCO)를 제작하였다. Ring VCO는 3단 구조로 각 단의 트랜지스터 크기 비율을 다르게 하여 전류 변화에 따른 소모 전력이 달라짐을 확인하였다. Core의 양단 위, 아래에는 Current Mirror로 전류를 제어하도록 구성하였고, 주파수 조절을 위해 제어 전압을 추가하였다. Ring VCO 측정 결과, 주파수 범위는 65.5 %(1.88~5.45 GHz), 출력 전력 -0.30 dBm, 5.08 GHz 중심주파수에서 -87.50 dBc/Hz @1 MHz의 위상잡음을 갖는다. 또한, 2.4 V 전원에서 31.2 mW 소모 전력을 확인하였다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2003년도 학술회의 논문집 정보 및 제어부문 A
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• pp.275-278
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• 2003

This paper presents a full-adder using current-mode multiple valued logic CMOS circuits. This paper compares propagation delay, power consumption, and PDP(Power Delay Product) compared with conventional circuit. This circuit is designed with a samsung 0.35um n-well 2-poly 3-metal CMOS technology. Designed circuits are simulated and verified by HSPICE. Proposed full-adder has 2.25 ns of propagation delay and 0.21 mW of power consumption.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2007년도 제38회 하계학술대회
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• pp.335-336
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• 2007

A new current-programmed pixel circuit for activematrix organic light emitting diodes (AMOLEDs), based on Organic TFTs (OTFTs), is proposed and verified by SPICE simulations. The simulation results show that the proposed pixel circuit, which is a current mirror structure consisting of five Organic TFTs and one capacitor, has reliable linear characteristics between input current and output OLED current. Also, the threshold voltage degradation of Organic TFTs due to long time operation stress is well compensated to reliable values.

• 대한전자공학회논문지SD
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• 제41권7호
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• pp.89-96
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• 2004

넓은 범위의 전압-제어 발진기 및 자동 이득 조절기의 실현을 위한 고선형 전압-제어 전류원(VCCS) 회로를 제안하였다. 제안한 VCCS는 전압 입력을 위해 이미터 폴로워, 전류 출력을 위해 이미터가 결합된 두 개의 공통-베이스 증폭기, 그리고 넓은 범위의 전류 출력과 높은 선형성을 얻기 위해 두 증폭기를 결합한 전류 미러로 구성된다. VCCS의 회로는 별도의 바이어스회로가 없이 단지 5개의 트랜지스터와 1개의 저항기만 사용하였다. 시뮬레이션 결과 제안한 VCCS는 5V의 공급전압에서 1V에서 4.8V까지의 제어-전압에 대하여 최대 0A에서 300㎃까지의 전류를 출력할 수 있다. 0㎃에서 300㎃의 출력 전류의 최대 선형 오차는 1.4 %이였다.

• 전기학회논문지
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• 제61권4호
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• pp.612-616
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• 2012

This paper presents an active current regulator for LED driver IC. The proposed driver circuit is consists of DC-DC converter for supplying constant DC voltage to LED, active current regulator for compensating channel-to-channel current error from LED strings and feedback circuit for controlling duty ratio of the converter. The proposed active current regulator senses current of LED channels by equalizing both $V_{DS}$ and $V_{GS}$ at LED current control transistor. Because the proposed circuit directly measures the LED channel current without a sensing resistor and regulates all channel with same regulation loop, the power consumption and the current error are much small compared with previous works. The measured maximum efficiency of overall LED driver IC is approximately 94% and current error of LED channel-to-channel is under ${\pm}1.3%$. The proposed LED driver IC is fabricated Dongbu 0.35um BCD process.

• 전자공학회논문지A
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• 제32A권11호
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• pp.29-34
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• 1995

Mirror coating is applied to laser facets to improve properties of edge emitting laser diodes. In this experiment, InGaAsP/GaAs high power laser diodes were studied with respect to different degrees of anti-reflective coating. Sputterred $Al_{2}$O$_{3}$ was used as the coating material and the HR coating was kept constant at 90%. Threshold current density, differential quantum efficiency, emission wavelength and the operating current at 500mW were measured for a range of AR coating and compared with theoretically calculated values; that showed good agreements. Precise wavelength control is important for laser diodes for solid state pumping because of small absorption bandwidth. In addition, since these lasers operate under CW condition, a lowest possible operating current for a given power is desired in order to minimize the heat produced. From the results of this experiment, we were able to obtain a optimum range of AR coatings for minimum operating current. The wavelength can be varied up to 4nm within this range.