• ETRI Journal
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• 제27권2호
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• pp.223-226
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• 2005

This paper presents the application of a turbo coding technique combined with a bandwidth efficient method known as trellis-coded modulation. A transformation applied to the incoming I-channel and Q-channel symbols allows the use of an off-the-shelf binary/quadrature phase shift keying (B/QPSK) turbo decoder without any modifications. A conventional turbo decoder then operates on transformed symbols to estimate the coded bits. The uncoded bits are decoded based on the estimated coded bits and locations of the received symbols.

• Journal of information and communication convergence engineering
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• 제14권4호
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• pp.227-232
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• 2016

In this study, the performance of a 32-quadrature amplitude position modulation (QAPM) system is analyzed under a Rician fading channel condition when the maximal ratio combining (MRC) diversity technique is used in the receiver. The fading channel is modeled as a frequency non-selective slow Rician fading channel corrupted by additive white Gaussian noise (AWGN). QAPM is available to improve BER performance without amplifying transmit power, and MRC diversity makes the performance improvement of QAPM system even bigger by intentionally maximizing SNR. Error performances are shown for the 32-QAPM system and a 32-phase silence shift keying (PSSK) system in order to examine the effects of fading severity, for various values of the Rician parameter, K. The dependence of error rates on MRC diversity is also analyzed. The simulation results show that the BER performance of the 32-QAPM system is better than that of the 32-PSSK system under the above mentioned conditions.

• 센서학회지
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• 제16권5호
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• pp.342-348
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• 2007

A high-speed signal processor for Fabry-Perot interferometric sensors using modified ramp modulation is implemented. The main idea for the signal processing is to find a modulation waveform that could induce a linear frequency change in a laser diode to linearize the relationship between the optical phase shift and measurand. It is found that the waveform could be modeled as the addition of a linear term and an exponential term. A signal processor adopting modified ramp modulation technique is implemented and evaluated to find linearity, drift and random walk of $<{\pm}1.5%$, $0.4^{\circ}C$, $5.28{\times}10^{-4}^{\circ}C/{\sqrt{Hz}}$.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2002년도 추계학술대회 논문집
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• pp.128-131
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• 2002

Three Dimensional measuring system using optical interference is greatly needed for semiconductor surface or optical surface. The application of this system are : MEMS product, semiconductor surfaces, optical components, precise machined surface, etc. In this paper, Interferometry based measurement system is introduced, which is nondestructive and noncontact inspection system. This system have relatively many advantage, compared with AFM/STM, SEM, Stylus, etc. The developed system can measure the surface topography with high precision and resolution, and with few seconds. And the associated software algorithm is also developed for the ultra precision 3D measuring surface. Various samples that is measured using this system is showed in the latter of this paper.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1988년도 전기.전자공학 학술대회 논문집
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• pp.705-708
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• 1988

Ultrasound Doppler Diagnostic System utilizes the Doppler effect for measurement of blood velocity. The sign of the Doppler frequency shift represents blood flow direction. Pulsed Doppler System uses Phase detector and zerocrossing method to produce simultaneous independent audio and velocity signals for forward and reverse blood flow direction in the time domain, had been fabricated. But time-domain analyzing such as audio evaluation and zerocrossing detection for instantaneous and mean frequency measurement doesn't, provide both an accurate and quantitative result. Therefore, it is necessary to adopt frequency domain technique to improve system performance. In this paper, we describe a unit which is composed of Pulsed Doppler System and real-time spectrum analyzer (installed TMS 32010 DSP Chip). This unit shows time-dependent spectrum variation and mean velocity of blood Signal.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1988년도 전기.전자공학 학술대회 논문집
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• pp.709-712
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• 1988

Ultrasonic Doppler Diagnostic System utilizes the Doppler effect for measurement of blood velocity. The sign of the Doppler frequency shift represents blood flow direction. CW(Continuous-Wave) Doppler System uses quadrature detection and phase rotation method to produce simultaneous independent audio and velocity signals for forward and reverse blood flow direction in the time-domain, had been fabricated. But time-domain analyzing such as audio evaluation and zero- crossing detection for instantaneous and mean frequnecy measurement do not provide both an accurate and quantitative result. Therefore, it is necessary to adopt frequency-domain technique to improve system performance. In this paper, we describe a unit which is composed of CW Doppler System and real-time spectrum analyzer (installed TMS 32010 DSP Chip). This unit shows time-dependent spectrum variation and mean velocity of Blood signal.

• The Journal of the Acoustical Society of Korea
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• 제24권3E호
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• pp.99-108
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• 2005

To investigate the equalizer performance in underwater acoustic communication m the presence of intersymbol interference (ISI) due to multipath, computer simulations are carried out in discrete multipath shallow water channels for three different horizontal ranges. For the purpose of computation simplicity, least mean square (LMS) algorithm is adopted both in linear equalizer and nonlinear equalizer, decision feedback equalizer (DFE) to cancel out ISI effects. Binary phase shift keying (BPSK) signals have been transmitted with high data rate of 2000bps through the use of equalization technique. The results demonstrate that equalization is an efficient way to achieve high transmission data rate in the shallow water channel.

• Journal of Advanced Marine Engineering and Technology
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• 제31권5호
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• pp.575-582
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• 2007

In this paper, a 100 Watt high power amplifier has been implemented and performed evaluation, which is operating at UHF band ($470\;{\sim}\;806\;MHz$) for Digital TV repeater. To achieve increase of bandwidth and high power capability, 3-way power combiner and divider of Wilkinson type was adopted. In order to measure the fabricated 100 Watt power amplifier, the estimation technique function which makes equivalent mask was used. As a result of the measurement, the existence of pilot signal is confirmed and the signal transmitted at the rated output power 100 Watt is brought out the flat feature through 6 MHz bandwidth. and it resulted that its value was less than -47 dB at the edge of radiation channel and less than -110 dB at more than 6 MHz position from channel edge.

• ETRI Journal
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• 제29권5호
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• pp.607-613
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• 2007

Most signal-to-noise ratio (SNR) estimation techniques in digital communication channels derive the SNR estimates solely from samples of the received signal after the matched filter. They are based on symbol SNR and assume perfect synchronization and intersymbol interference (ISI)-free symbols. In severe channel distortion where ISI is significant, the performance of these estimators badly deteriorates. We propose an SNR estimator which can operate on data samples collected at the front-end of a receiver or at the input to the decision device. This will relax the restrictions over channel distortions and help extend the application of SNR estimators beyond system monitoring. The proposed estimator uses the characteristics of the second order moments of the additive white Gaussian noise digital communication channel and a linear predictor based on the modified-covariance algorithm in estimating the SNR value. The performance of the proposed technique is investigated and compared with other in-service SNR estimators in digital communication channels. The simulated performance is also compared to the Cram$\acute{e}$r-Rao bound as derived at the input of the decision circuit.

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part 1
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• pp.53-54
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• 2006

Ti-Zr-Ni coatings deposited by low vacuum plasma spray technique consisted of nanometer-sized $W-Ti_{50}Zr_{35}Ni_{15}$ 1/1 cubic approximant and TiZrNi Laves phases as well as a low volume fraction of $ZrO_2$ phase. The shift of composition during deposition of the quasicrystalline powders and the presence of $ZrO_2$ phases are believed to be responsible for the reduced corrosion performances evaluated by means of electrochemical tests in a Hanks' Balance Salt Solution at $37^{\circ}C$.