• Proceedings of the Optical Society of Korea Conference
• /
• 2003.02a
• /
• pp.320-321
• /
• 2003

위성통신 및 무선통신에서 안테나의 수신 감도를 향상시키기 위한 노력은 계속되어 왔다. 안테나의 지향성을 높이기 위하여 다수의 동형 단위 안테나들을 일정 방향으로 배열하여 안테나를 기계적으로 회전시키지 않고, 고정된 다수의 동형 단위 안테나들에서 방사되는 전파의 위상을 전자적으로 변화시켜 방사 빔을 주사하는 방법, 즉 위상배열 안테나(Phased Array Antenna)를 널리 사용하고 있다. 위상배열 안테나의 단위 안테나에서 방사되는 전파의 위상을 변화시키기 위해선 실시간 시간지연 시스템이 필요하다. (중략)

• Journal of Communications and Networks
• /
• v.6 no.2
• /
• pp.147-155
• /
• 2004

In this paper, we propose an efficient sequencing technique, namely minimum Row time scheduling (MFTS), to manage variable-Iength message transmissions for single-hop passive starcoupled WDM optical networks. By considering not only the message length but also the state of the receivers and the tuning latency, the proposed protocol can reduce the average delay of the network greatly. This paper also introduces a new channel assignment technique latency minimizing scheduling (LMS), which aims to reduce the scheduling latency. We evaluate the proposed algorithm, using extensive discrete-event simulations, by comparing its performance with shortest job first (SJF) algorithm. We find that significant improvement in average delay could be achieved by MFTS algorithm. By combining the proposed message sequencing technique with the channel selection technique, the performance of the optical network could be further improved.

• Korean Journal of Optics and Photonics
• /
• v.21 no.5
• /
• pp.206-213
• /
• 2010

We fabricated and characterized a compact endoscopic catheter for optical coherence tomography. The optical delay line (ODL), composed of a cylindrical piezoelectric transducer (PZT) and an optical fiber, was operated with a 1 kHz sinusoidal driving wave in the time-domain. When the ODL was driven with a sinusoidal wave function, the axial scanning speed was 6 m/s and the axial acquisition rate was 2000 line/s at a depth of about 3 mm. Endoscopic OCT images of a human finger and earhole were successfully obtained with an image rate of ten frames per second.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.17 no.6
• /
• pp.539-547
• /
• 1992

Considering the field of high frequency or broad-band signal filtering with high speed, we pro-pose optical fiber filters which consist of directional couplers and optical fiber delay elements. Fiber delay line signal processor Is operated with Incoherent optical carrier because of Its simplicity. Due to the characteristics of the directional coupler which Is basic element of optical fiber filter a new design method which Is different from that of usual digital filter is required. By considering the characteristics of directional coupler and in order to make good use of the optical signal energy, we have given the design formulae and the conditions of optical fiber filters for the direct and the lattice form.

• Proceedings of the Optical Society of Korea Conference
• /
• 2008.07a
• /
• pp.277-278
• /
• 2008

• Proceedings of the Optical Society of Korea Conference
• /
• 2004.07a
• /
• pp.8-9
• /
• 2004

• Proceedings of the Optical Society of Korea Conference
• /
• 2009.10a
• /
• pp.373-374
• /
• 2009

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.18 no.3
• /
• pp.206-211
• /
• 2005

The device makers want to make higher density chips on the wafer through scale-down. The change of WSix/poly-Si gate film thickness is one of the key issues under 100 nm device structure. As a new device etching process is applied, end point detection(EPD) time delay was occurred in DPS+ poly chamber of Applied Materials. This is a barrier of device shrink because EPD time delay made physical damage on the surface of gate oxide. To investigate the EPD time delay, the experimental test combined with OES(Optical Emission Spectroscopy) and SEM(Scanning Electron Microscopy) was performed using patterned wafers. As a result, a EPD delay time is reduced by a new chamber seasoning and a new wavelength line through plasma scan. Applying a new wavelength of 252 nm makes it successful to call corrected EPD in WSix/poly-Si stack-down gate etching in the DPS+ poly chamber for the current and next generation devices.

• Korean Journal of Optics and Photonics
• /
• v.16 no.2
• /
• pp.133-137
• /
• 2005

A photonic RF true-time delay using a tapered chirped fiber Bragg grating coated with a heating electrode has been proposed and fabricated. For an RF signal carried over an optical signal, the time delay has been achieved by controlling the voltage applied to the electrode and thus adjusting its reflection positions from the fiber grating through the thermooptic effect. It features continuous voltage-controlled operation, requiring no mechanical perturbation and no moving parts. The measured time delay was about 120 ps with the electrical power consumption of $250{\cal}mW$.

• Journal of the Institute of Electronics Engineers of Korea CI
• /
• v.43 no.4 s.310
• /
• pp.23-30
• /
• 2006

This paper presents design andd verification of a circuit that improves the control-operation problems of Stored Program Optical Computer (SPOC), which is an optical computer using $LiNbO_3$ optical switching element. Since the memory of SPOC takes the Delay Line Memory (DLM) architecture and instructions that are needless of operands should go though memory access stages, SPOC memory have problems; it takes immoderate access time and unnecessary operations are executed in Arithmetic Logical Unit (ALU) because desired operations can't be selectively executed. In this paper, improvement on circuit has been achieved by removing the memory access of instructions that are needless of operands by decoding instructions before locating operand. Unnecessary operations have been reduced by sending operands to some specific operational units, not to all the operational units in ALD. We show that total execution time of a program is minimized by using the Dual Instruction Register(DIR) architecture.