• 한국정보디스플레이학회:학술대회논문집
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• 2004.08a
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• pp.561-563
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• 2004

In this paper, distortion of waveform in AC-PDP module has been studied. The propagation losses and interference due to coupling between the electrodes can be considered as the causes for waveform distortion. The distorted waveform has been obtained from the calculated propagation losses. The coupling between the electrodes has been measured using a proper experimental setup. This distorted waveform could account for underfiring problem in AC PDP module.

• Journal of Advanced Navigation Technology
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• v.23 no.6
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• pp.522-525
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• 2019

To overcome the limitation of ground inspection for Navigational Aid, Korea Airport Corporation (KAC) developed a drone system for Navigational Aid inspection. This drone system has the advantage that they can inspect the air radio signal at the perspective of user (aircraft). Since drones have more free flight paths and easier control of flight speeds compared to aircrafts, drones can check sections of suspected airborne radio wave distortions at desired paths and speeds. Recently, with the acceleration of the development around the airport, there is a concern about the deterioration of the quality of radio signal of Navigational Aid. In order to analyze radio distortion of Navigational Aid, a radio wave environmental survey was conducted using drones. When the signal received by each flight path of the drone was measured, the origin of the reflected wave was identified by analyzing the section in which the radio signal was distorted.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.10A
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• pp.935-942
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• 2006

The performance of ROF systems can be severely degraded due to nonlinear effects in the channel. Also, Orthogonal Frequency Division Multiplex(OFDM), as a standard for broadband wireless and mobile internet networks, is being proposed for deployment with ROF systems to facilitate the total performance of a system. In this paper, at first, the performance of the OFDM-based RoF system with a Mach-Zehnder(MZ) modulator distortion effects has been analyzed at 5.8GHz. Evaluation of mean-squared error of the proposed OFDM-RoF system was carried out to compare with the conventional single carrier system based RoF link after the modulator distortion case and also for fixed signal to noise ratio(SNR) of 20dB using undistorted OFDM signal. Nominal and offset baising pre-distortion techniques are applied in proposed system to linearize the OFDM-RoF link. Finally, a comparison between the aforementioned pre-distortion techniques applied showed important observation in terms of distortion-free dynamic range and SNR to choose offset pre-distortion technique for our proposed system.

• Journal of information and communication convergence engineering
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• v.10 no.3
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• pp.300-306
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• 2012

An image attention model and its application to image quality assessment are discussed in this paper. The attention model is based on rarity quantification, which is related to self-information to attract the attention in an image. It is relatively simpler than the others but results in taking more consideration of global contrasts between a pixel and the whole image. The visual attention model is used to develop a local distortion predictor, named color visual differences predictor (CVDP), in color images in order to effectively detect luminance and color distortions.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.38 no.5
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• pp.1-8
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• 2001

This paper presents the analysis of fiber radio system transmitting OFDM signal. We propose a baseband equivalent system model and prove the relation between the IMD(intermodulation distortion) power and the number of subcarrier in the OFDM signal. Using this relation, we derive the CNH of the overall system. In terms of the required CNR for each digital modulation scheme, we extract the maximum number of the subcarrier in the OFDM signal using simulation and examine how the system parameters are related with the CNR.

• The Journal of the Acoustical Society of Korea
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• v.17 no.4E
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• pp.35-40
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• 1998

In this paper, an efficient quantization method of line spectrum pairs(LSP) with cascaded structure of vector quantizer and scalar quantizer is proposed. First, input LSP parameters is vector-quantized using a codebook a with a moderate number of entries. In the second stage of quantization, the components of residual vector are individually quantized by the scalar quantizer. The utilization of ordering property of LSP parameters and the inclusion of interframe prediction improve the quantizer performance and remove the stability check routine after quantization procedure. The new vector-scalar hybrid quantizer using 26 bits/frame shows a transparent quality of speech that an average spectral distortion is 1 dB and the frame proportion with above 2 dB spectral distortion is less than 2%. The performances of proposed quantization method is evaluated in the transmission errors.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.60 no.4
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• pp.823-828
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• 2011

We have systematically designed and experimentally demonstrated the opto-electrical predistortion optical transmitter using microwave circuit modelling for reducing the nonlinearity of the distributed-feedback laser diode (DFD-LD). The DFB-LD is analyzed using microwave circuits model based on rate equations. Through the system-level simulation for predistortion method, the optimized characteristics of the RF components in the system are confirmed. The simulated and experimental results show the reduced distortion products. These results are analyzed as the evaluation parameters for the miniaturization and optimization of the opto-electrical predistortion method in radio-over-fiber systems.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.11 no.5
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• pp.103-115
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• 2012

In this paper, design and performance evaluation of Tapered Slot Antenna for IR-UWB which propagates impulse radio is performed. TSA which has directional characteristic in UWB band should have low radiation loss and minimized impulse radiation distortion. In order to achieve these objectives, the paper designed wide band Impedance transformer and microstrip-slotline transit region structured TSA feeder line. By using the fabricated TSA, the radiation pattern was measured in the radio anechoic chamber. Pulse fidelity and distortion equation was induced to evaluate time domain characteristics according to the impulse radiation. Pulse fidelity of Impulse radiation show favorable results more than 93% within ${\pm}30^{\circ}$ beam width.

• Journal of Advanced Navigation Technology
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• v.8 no.2
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• pp.91-97
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• 2004

This paper presents the development of InGaAsP multiple quantum well asymmetric Fabry-Perot modulators(AFPM), which have a vertical structure and high performance and describes measurements of devices operating at 10GHz for next generation broadband wireless communication applications such as picocell systems. Advantages of the AFPM include low drive voltage, which is less than -2V, and -3dB coupling loss, good flatness of the frequency response and simple fiber alignment. A simple link demonstration has been introduced, resulting in 92dB/Hz spurious free dynamic range and 40dB inter-modulation distortion. This modulator could be use for broadband radio over fiber systems such as picocell and multiple RF links.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.10 no.9
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• pp.2261-2266
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• 2009

A novel adaptive phase calibration method is proposed for nonlinear amplifiers. Based on the adaptive process of simple phase vector calculations, the AM/PM distortion can be significantly reduced for various input power. The performance of the proposed method is evaluated for up to 80 % improvements in AM/PM distortions, compared with the distortion of a conventional amplifier. Moreover, by means of an additional envelope-compensation technique, the improvement of the adjacent channel power ratio (ACPR) is presented.