• Title/Summary/Keyword: heterodyne system

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Adaptive Nonlinearity Compensation in Laser Interferometer using Neural Network (신경망 회로를 이용한 레이저 간섭계의 적응형 오차보정)

  • Heo, Gun-Hang;Lee, Woo-Ram;You, Kwan-Ho
    • Proceedings of the KIEE Conference
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    • 2007.04a
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    • pp.86-88
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    • 2007
  • In the semiconductor manufacturing industry, the heterodyne laser interferometer plays as an ultra-precise measurement system. However, the heterodyne laser interferometer has some unwanted nonlinearity error which is caused from frequency-mixing. This is an obstacle to improve the measurement accuracy in nanometer scale. In this paper we propose a compensation algorithm based on RLS(recursive least square) method and artificial intelligence method, which reduce the nonlinearity error in the heterodyne laser interferometer. With the capacitance displacement sensor we get a reference signal which can be transformed into the intensity domain. Using the back-propagation Neural Network method, we train the network to track the reference signal. Through some experiments, we demonstrate the effectiveness of the proposed algorithm in measurement accuracy.

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Overcoming OBI Problem by Means of Heterodyne Detection in Upstream Transmission of WDM/SCM-PON (WDM/SCM-PON의 상향 전송에서 헤테로다인 방식을 이용한 광간섭잡음 문제 극복방안 연구)

  • Jeon, You-Chan;Shin, Hong-Seok;Park, Jin-Woo
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.35 no.2A
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    • pp.202-208
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    • 2010
  • The performance of upstream transmission in SCM-PON is generally limited by the presence of OBI which is caused by the beating of two or more lasers. In this paper, we propose a novel approach for reducing OBI problem by using heterodyne detection with an additional LD as a local oscillator, resulting that the RF signal is shifted to the other spectal band. In addition, it is possible that the proposed method can provide the cost-effective solution thanks to the loop-back mechanism using R-SOA in ONUs. The performance is superior when the spectral width of LD is smaller and the power difference between the transmission LD and the oscillation LD is bigger. System configuration and design consideration are discussed. Performance of the systems is evaluated by simulator called OptSim. It is expected to provide WDM/SCM-PON system not only cost-effective but also efficient in increasing the number of subscribers.

Design and Fabrication of Super Heterodyne AM Tuner System for CAR (자동차용 Super Heterodyne AM 수신기의 설계 및 제작)

  • Shin, Young-Ho;Choi, Du-Hwan;Kang, Dae-Bong
    • Proceedings of the KIEE Conference
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    • 1987.07b
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    • pp.1221-1224
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    • 1987
  • In this paper, we had designed and fabricated the integrated circuit of AM tuner system for car. The very important characteristics of this system need very good sensitivity, selectivity and very strong automatic gain control function. In this system we had designed, maximum sensitivity is about 21dBu, selectivity above 40dB, AGC range above 80dB, etc. We had fabricated this IC using SST standard linear process.

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Absolute Measurement of the Refractive Index of Air Using the Heterodyne Interferometer (Heterodyne 간섭계를 이용한 공기굴절율의 절대측정)

  • 엄태봉;엄천일;정명세;양준묵
    • Korean Journal of Optics and Photonics
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    • v.7 no.1
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    • pp.37-43
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    • 1996
  • Two type interference air refractometers have been developed by using a frequency stabilized He-Ne laser in a transverse magnetic field. The refractometers were based on symmetric multiple pass interferometer. In this system, One part of the beams passed through air whose refractivity is to be measured and the other part of the beams passed through a vacuum champer to be used as a reference. Several measurements were performed under normal air condition. Maximum difference between two interference refractometers was ${\pm}2{\times}10^{-8}$.

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Development of Acoustic Emission(AE) Sensor for Prognosis Detection of Bearing Fault (베어링 고장 예후검출을 위한 음향 방출(AE)센서 개발)

  • Lee, Chibum;Kim, Gyeongwoo;Park, Yeong-Il
    • Transactions of the Korean Society for Noise and Vibration Engineering
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    • v.24 no.6
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    • pp.429-436
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    • 2014
  • Most mechanical systems are now operating consistently and getting faster due to the development of automation systems. Peoples' dependence on machines have increased as when problems occur within the mechanical system, personal injury and production loss may come as a result, as most of the mechanical system's malfunctions are caused by the failure of the rotational bearing. What we need now is a maintenance system that can warn us when it detects abnormal conditions before significant damage occurs to the bearing. In this study, we have developed an acoustic emissions sensor that can figure if the bearing works under the normal condition. With this acoustic emissions sensor, we can inspect the bearing for defects by using the Heterodyne technique, which converts the ultrasound signal into audio, as a signal conditioning process.

A 1.485 Gbps Wireless Video Signal Transmission System at 240 GHz (240 GHz, 1.485 Gbps 비디오신호 무선 전송 시스템)

  • Lee, Won-Hui;Chung, Tae-Jin
    • The Journal of the Institute of Internet, Broadcasting and Communication
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    • v.10 no.4
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    • pp.105-113
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    • 2010
  • In this paper, a 1.485 Gbps video signal transmission system using the carrier frequency of 240 GHz band was designed and simulated. The sub-harmonic mixer based on Schottky barrier diode was simulated in the transmitter and receiver. Both of heterodyne and direct detection receivers were simulated for each performance analysis. The ASK modulation was used in the transmitter and the envelop detection method was used in the receiver. The transmitter simulation results showed that the RF output power was -11.4 dBm($73{\mu}W$), when the IF input power was -3 dBm(0.5 mW) at the LO power of 7 dBm(5 mW) in sub-harmonic mixer, which corresponds to SSB(Single Side Band) conversion loss of 8.4 dB. This value is similar to the conversion loss of 8.0 dB(SSB) of VDI's commercial model WR3.4SHM(220~325 GHz) at 240 GHz. The combined transmitter and receiver simulation results showed that the recovered signal waveforms were in good agreement to the transmitted 1.485 Gbps NRZ signal.

Adaptive Error Compensation of Heterodyne Laser Interferometer using DFNN (DFNN을 이용한 헤테로다인 레이저 간섭계의 적응형 오차 보정)

  • Heo, Gun-Haeng;Lee, Woo-Ram;You, Kwan-Ho
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.57 no.6
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    • pp.1042-1047
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    • 2008
  • As an ultra-precision measurement system the heterodyne laser interferometer plays an important role in semiconductor industry. However the errors of environment and nonlinearity which are caused by air refraction and frequency-mixing separately reduce the accuracy of displacement measurement. In this paper we propose a DFNN(data fusion and neural network) method for error compensation. As a hybrid method of data fusion and neural network, DFNN method reduces the environmental and nonlinear error simultaneously. The effectiveness of the proposed error compensation method is proved through experimental results.

A Study on the Optical Communication System using Heterodyne Detection Method(Design of Thermal Chamber for LD Frequency Stabilization) (헤테로다인검파방식을 이용한 광통신시스템에 관한 연구 (LD의 주파수안정화를 위한 항온기설계 에 관하여))

  • 임명섭;홍완희;박한규
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.10 no.4
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    • pp.168-174
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    • 1985
  • The wavelength and output power of semiconductor laser is varying sensitively with temperature. It must be stabilized by the aid of some proper stabilization technique in order to use it as a radiative source for heterodyne optical communication, optical metrology, and high resolution spectroscopy. In this paper, the temperature of the thermal chamber was variable from -27$-50^{\circ}C$ to +73$-50^{\circ}C$ and the temperature stability was within ${\pm}2m{\circ}K$ or better.

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Millimeter-wave signal Generation using Heterodyne Technique (헤테로다인 기법을 이용한 밀리미터파 신호 생성)

  • 김정태
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.7 no.6
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    • pp.1334-1340
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    • 2003
  • In this paper, We have proposed an Heterodyne technique to generate millimeter-wave signal. Microwave signals in cellular broadband mobile communication networks and distributed networks can favorably be generated and distributed by optical techniques. In principle, these techniques have already been investigated for optical control of phase- array antennas, characterization of photo-detector and phase locking of millimeter-wave oscillators and now being applied to wireless communications. The generation and transmission of millimeter-wave radio signals by optical means is of interest for future pico-cell broadband mobile communication system, especially for systems operating at frequencies of 300Hz.

A Design for a Home-Built Solid State NMR Spectrometer

  • Yang Doo-Kyung;Zax David B.
    • Journal of the Korean Magnetic Resonance Society
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    • v.10 no.1
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    • pp.74-88
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    • 2006
  • Since the first commercial NMR spectrometer came out in 1953 from Varian, much of the hardware development has been improved and matured through commercial equipments. Many of magnetic resonance laboratories however still build and use home-built spectrometers, which are satisfactory even with the consideration of educational purpose only. The home-built NMR spectrometer could be further advantageous and could be often an only option for investigating new ideas with demanding experimental conditions or new hardware support. A solid state NMR spectrometer was designed with extra interest in stochastic experiment and built for an 8.93 T superconducting magnet from Oxford instrument. Super-heterodyned system was implemented for the transmitter and receiver parts. Intermediate frequency (IF) for the heterodyne system was chosen to 70 MHz for the first and the second channels, with additional 120 MHz for the third channel for maximum NMR frequency capability. We will show overall schematics, and discuss the designs with detailed diagrams, then demonstrate the applicability of home-built spectrometer with stochastic-excitation in solid state NMR and in applications to quadrupolar nuclear Spins.

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