• 소음진동
• /
• 제7권6호
• /
• pp.931-936
• /
• 1997

Optical fiber sensor is a subject which has been attracted considerable attention in recent years. Detection of sound pressure with optical fibers positioned in the arms of a Mach-Zehnder interferometer is presented in this paper. A fiber length of the order of 150m is wounded is made by hollow cylinder type. To increase the sound signal 3${\times}3$ directional coupler is used. Fiber optic hydrophone is the underwater tank with 2kHz sound source. Finally, it is shown that the fiber optic hydeophone can stably detec 2kHz sound.

• 한국음향학회지
• /
• 제8권1호
• /
• pp.75-80
• /
• 1989

단일모드 광섬유를 이용하여 호모다인 검출방식으로 동작하는 Mach-Zehner 광섬유 간섭계를 구성하여 공기중 음압반응을 조사하였다. 광섬유 간섭계 센서가 직각조건에서 동작하도록 하기 위해 기준 광섬유에 원통형 압전신장기를 사용하는 신호안정화 장치를 제작하였다. 이는 온도변화나 주위환경의 영향에 관계없이 광섬유 간섭계 센서의 감도를 최대의 크기로 일정하게 유지시켜 준다.

• 한국통신학회논문지
• /
• 제33권7A호
• /
• pp.751-756
• /
• 2008

In this paper, we propose a modified I/Q diversity scheme receiver of UHF RFID reader system. The modified I/Q diversity receiver is more robust than the conventional homodyne receiver in the wireless noisy, fading channel and phase noise environments by making use of additional axes. In particular, it is shown that the closer the phase difference ${\theta}(t)$ between the reader and the tag to ${\pi}/4$, the larger performance improvement we can get. The performance of the proposed receiver is verified by equations and is demonstrated by the computer simulation for various difference ${\theta}(t)$ cases.

• 제어로봇시스템학회:학술대회논문집
• /
• 제어로봇시스템학회 1989년도 한국자동제어학술회의논문집; Seoul, Korea; 27-28 Oct. 1989
• /
• pp.547-552
• /
• 1989

Single mode optical fiber interferometeric sensors using phase tracking homodyne detection are typically susceptible to environmentally induced temperature fluctuations and other types of disturbances. In this paper compensator is described, which is a simple and effective phase tracking feedback electronic circuit must be output signal stabilized to achieve maximln sensitivity and linearity of Mach-Zehnder fiber-optic interferomter in the presence of differential phase drift. The phase tracking range of the piezoelectric cylinder in the reference arm is .+-.3.7.pi.rad, and the probe mass about 1 gram in the sensing ann was used for measurements of the gravity acceleration.

• 한국광학회지
• /
• 제6권1호
• /
• pp.62-69
• /
• 1995

레이저 다이오드 구동 전류펄스기간의 발진주파수 변조와 간섭계 출력신호의 시간지연 샘플링을 이용하여 3x3 coupler등과 같은 특수 광부품을 사용하지 않고도 1개씩의 광원과 광검출기를 이용하여 측정신호의 변화방향과 함께 half fringe의 수를 count할 수 있으며 광연결선 주변환경의 변화에 의한 세기변화 에러도 피할 수 있는 간섭형 센서를 위한 새로운 신호처리방식을 제안하고 이 방식을 거울내장형 FP간섭계를 이용한 온도센서에 적용하였다. 온도센서소자로 cavity length가 1cm인 FP간섭계를 이용하여 실온에서 360.deg.C에 걸쳐 분해능 2.7.deg.C로 측정하였으며 이때 최대측정속도는 $ 1.378*10^{5}$.deg.C/sec로 계산되었다. 이 방식에서 분해능과 최대측정속도는 반비례 관계를 가지며 감지 광섬유의 길이에 비례하여 분해능을 높일 수 있다. 또한 6개까지의 센서소자를 한개의 광원과 광검출기로 모니터하는 다중화 센싱 또한 가능한 신호처리 방식으로써 불평형 간섭계를 이용한 모든 종류의 센서에 대해 적용이 가능하다.

• 한국정밀공학회지
• /
• 제16권10호
• /
• pp.203-208
• /
• 1999

By tilting the reference mirror of Twynman-Green interferometer having a reference mirror and a moving mirror, firinge pattern composed of bright and dark parallel lines can be obtained and the fringe pattern is shifted according to the displacement of the mowing mirror. Several studies are executed for displacement measurement by detecting the intensity of the fringe with photo-diodes having small detecting area. In this study, to improve the sensitivity and robustness, the intensity of fringe is detected by using a large-area quadratic photo-diode masked with a grating panel having four kinds of binary grating having phase-difference of 0, {\pi}$/4, {\pi}$/2, 3 {\pi}$/4. The phase of the fringe is calculated with a simple 4-buckets algorithm. A experimental result shows that standard deviation of 5.653 nm is obtained comparing with a capacitive type gap sensor having nearly 1 nm accuracy.

• Journal of Communications and Networks
• /
• 제4권4호
• /
• pp.344-350
• /
• 2002

This work summarizes the current state of the art in software radio for 4G systems. Specifically, this work demonstrates that classic radio structures, e.g., heterodyne reception, homodyne reception, and their improved implementations, are inadequate selections for multi-mode reception. This opens the door to software defined radio, a novel reception architecture which promises ease in multi-band, multi-protocol design. The work presents the many advantages of such an architecture, including flexibility, reduced cost via component reduction, and improved reliability via, e.g., the elimination of environmental instability. The work also explains the limitations that currently curtail the widespread use of SDR, including issues surrounding A/D converters, management of software and power, and clock generation. This provides direction for future research to enable the broad applicability of SDR in 4G cellular and beyond.

• 반도체디스플레이기술학회지
• /
• 제3권2호
• /
• pp.41-46
• /
• 2004

This paper proposes a robust discrete time Kalman filter (RDKF) for the dynamic compensation of nonlinearity in a homodyne laser interferometer for high-precision displacement measurement and in real-time. The interferometer system is modeled to reduce the calculation of the estimator. A regulator is applied to improve the robustness of the system. An estimator based on dynamic modeling and a zero regulator of the system was designed by the authors of this study. For real measurement, the experimental results show that the proposed interferometer system can be applied to high precision displacement measurement in real-time.

• 대한전자공학회논문지
• /
• 제26권12호
• /
• pp.2032-2038
• /
• 1989

Single mode optical fiber interferometeric sensors using phase tracking homodyne detection are typically susceptible to environmentally indured temperature fluctuations and other types of disturbances. A simple and effective phase tracking feedback electronic circuit for compensator is described to achieve stabilizing signal output, maximum sensitivity and linearity in the fiber optic Mach-Zehnder infterferometer in the presence of differential phase drift. The phase tracking range of the piezoelectric cyclinder in the reference arm is \ulcorner.7 \ulcornerad and the prabe mass about 1 gram in the sensing arm was used for measurements of the gravity acceleration.

• 한국통신학회논문지
• /
• 제22권5호
• /
• pp.899-906
• /
• 1997

It is known that the Differential Phase Shift Keying (DPSK) modulation scheme in the coherent optical communication system is suitable for design of long-distance transmission system because its receiver performance is 3-5dB better than ASK and FSK. In this paper, we descrive a fundamental understanding of the effects of laser phase noise on the performance of coherent lighwave communication systems. Formulas are derived for the bit error rate in homodyne and heterodyne DPSK. Based on detailed mathematical analysis and estimates, we explain the following finding. DPSK can operates at rates only 300 times greater than the laser linewidth.