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Co-Simulation for Systematic and Statistical Correction of Multi-Digital-to-Analog-Convertor Systems
Youngcheol Park,Hoijin Yoon 한국전자파학회JEES 2017 Journal of Electromagnetic Engineering and Science Vol.17 No.1
In this paper, a systematic and statistical calibration technique was implemented to calibrate a high-speed signal converting system containing multiple digital-to-analog converters (DACs). The systematic error (especially the imbalance between DACs) in the current combining network of the multi-DAC system was modeled and corrected by calculating the path coefficients for individual DACs with wideband reference signals. Furthermore, by applying a Kalman filter to suppress noise from quantization and clock jitter, accurate coefficients with minimum noise were identified. For correcting an arbitrary waveform generator with two DACs, a co-simulation platform was implemented to estimate the system degradation and its corrected performance. Simulation results showed that after correction with 4.8 Gbps QAM signal, the signal-to-noise-ratio improved by approximately 4.5 dB and the error-vector-magnitude improved from 4.1% to 1.12% over 0.96 GHz bandwidth.
Arbitrary Sampling Method for Nonlinearity Identification of Frequency Multipliers
Youngcheol Park,Hoijin Yoon 한국전자파학회JEES 2008 Journal of Electromagnetic Engineering and Science Vol.8 No.1
It is presented that sampling rates for behavioral modeling of quasi-memoryless nonlinear devices can be far less than the Nyquist rate of the input signal. Although it has been believed that the sampling rate of nonlinear device modeling should be at least the Nyquist rate of the output signal, this paper suggests that far less than the Nyquist rate of the input signal can be applied to the modeling of quasi-memoryless nonlinear devices, such as frequency multipliers. To verify, a QPSK signal at 820 ㎒ were applied to a frequency tripler, whereby the device can be utilized as an up-converting mixer into 2.46 ㎓ with the aid of digital predistortion. AM-AM, AM-PM and PM-PM can be successfully measured regardless of sampling rates.
Youngcheol Son,Kyongku Yun,Seungyeon Han 한국도로학회 2018 한국도로학회 학술대회 발표논문 초록집 Vol.2018 No.05
In this thesis, it was considered that in durability characteristics of concrete pavements evaluation of strength characteristics as well as abrasion resistance is important as the domestic concrete pavements couldn't fulfill the public needs and cases of damage are increasing. In order to solve such problems, it is intended to compare the abrasion resistance in accordance with the mixing rate of admixtures (silica fume and polymer powder) which are incorporated in the upper layer of two-lift concrete pavement and find the optimum mixing rate for abrasion resistance by focusing on the high performance of concrete pavements through two-lift concrete pavements which use cellular sprayed concrete construction method. Both test results, which were performed based on ASTM C 779 B (dressing wheel abrasion test method) and ASTM C 944 (rotary cutter method) standards in accordance with silica fume and polymer powder mixing rate that was incorporated in the upper layer of two-lift concrete pavement, proofed that the abrasion resistance increased as the mixing rate of silica fume and polymer powder increased. However, it was also confirmed that if the mixing rate of admixtures is excessively increased it will not have an effect and it will rather decrease the abrasion resistance.
Minimization of Peak Current-Consumption in mobile-WiMAX and CDMA-cellular, Dual-mode Handsets
Youngcheol Park 대한전자공학회 2007 ITC-CSCC :International Technical Conference on Ci Vol.2007 No.7
Peak power consumption is estimated in dualmode dual-band handsets with mobile WiMAX (mWiMAX) and CDMA cellular functions. Due to the limited power-supplying capacity of batteries, dualoperatoin such as voice-call paging on a CDMA cellular network whilst a video conferencing through a mWiMAX network necessiates a precise power management for successful dual-mode handset-system design. Therefore, peak power consumptions for major blocks (mWiMAX, CDMA, Video processor block and etc) in DBDM handsets were estimated, and a peak-off capacitor is suggested to prevent from the potentially demaging peak values by reducing the peaking current during the transmit period in a TDD frame of the mWiMAX system.