• Journal of Power Electronics
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• v.15 no.3
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• pp.670-684
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• 2015

The hybrid cascaded multilevel inverter (HCMLI) is a popular converter topology that is being increasingly used in high power medium voltage drives. The intricacy of the control technique for a HCMLI increases with the number of levels and due to fluctuating dc voltages. This paper presents a novel offline quadrant search based space vector modulation technique to synthesize a sinusoidal output from a dispersed pattern of voltage vectors due to different voltages in the auxiliary unit. Such an investigation has never been reported in the literature and it is being attempted for the first time. The method suggested distributes the voltage vectors for a reduced total harmonic distortion at minimal computation. In addition, the proposed algorithm determines the maximum modulation index in the linear modulation range in order to synthesize a sinusoidal output for both normal and abnormal vector patterns. It is better suited for a wide range of practical applications. It is particularly well suited for renewable source fed inverters which utilize large capacitor banks to maintain the dc link, which are prone to such slow fluctuations. The proposed quadrant search space vector modulation technique is simulated using MATLAB/SIMULINK and implemented using a Nexys-2 Spartan-3E FPGA for a developed prototype.

• Proceedings of the IEEK Conference
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• 2005.11a
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• pp.221-224
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• 2005

This paper discribes the nonlinear distortion of a pHEMT power amplifier. In the paper, we have used some commercially available power amplifiers for analyzing the relationship between the $IMD_3$ and ACPR for wireless LAN. And the $IMD_3$ results using two-tone test have been compared with ACPR to satisfy the requited 802.11g standard ACPR value. Measurement result shows that $IMD_3$ of 20MHz tone-spacing need to be more than 18.45dBc for power amplifiers. The WCDMA signal is fed into the power amplifier, for analyzing relationship between the asymmetrical $IMD_3$ and ACLR. With measurement result, the asymmetrical $IMD_3$ characteristic has increased with the increase of two-tone spacing. $IMD_3$ measurement result with maximum 20MHz of the two-tone spacing, shows that the difference between $IMD_3(lower)$ and $IMD_3(upper)$ is about 7dB. And the measured ACLR shows 5dB difference at -4MHz and +4MHz offset from center frequency.

• JSTS:Journal of Semiconductor Technology and Science
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• v.16 no.2
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• pp.185-190
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• 2016

A 70-${\AA}$ nanowire field-effect transistor (FET) for sub-10-nm CMOS technology is designed and simulated in order to investigate the impact of an oxide trap on random telegraph noise (RTN) in the device. It is observed that the drain current fluctuation (${\Delta}I_D/I_D$) increases up to a maximum of 78 % due to the single electron trapping. In addition, the effect of various trap positions on the RTN in the nanowire FET is thoroughly analyzed at various drain and gate voltages. As the drain voltage increases, the peak point for the ${\Delta}I_D/I_D$ shifts toward the source side. The distortion in the electron carrier density and the conduction band energy when the trap is filled with an electron at various positions in the device supports these results.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.14 no.5
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• pp.44-51
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• 2015

The deployment of high capacity backhaul is required due to explosive growth in mobile data services. For rapid backhaul deployment, point to point microwave is a much easier and cheaper technology. The space diversity scheme is used in point to point microwave links. The purpose of space diversity is to overcome fading by combining signals from two separate receiver antennas. For signal combining algorithm, maximum power and minimum distortion methods were used and these algorithms were reported not to be good enough for robustness in selective fading. In this paper, a more practically efficient signal combining scheme from the main and diversity branch is proposed and evaluated in selective fading channel. The proposed algorithm has shown significant performance improvement in terms of signal spectrum.

• IEIE Transactions on Smart Processing and Computing
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• v.4 no.3
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• pp.189-193
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• 2015

This paper provides the design techniques of a successive approximation register (SAR) type 12b analog-to-digital converter (ADC) for distributed maximum power point tracking (DMPPT) control in a photovoltaic system. Both a top-plate sampling technique and a $V_{CM}$-based switching technique are applied to the 12b capacitor digital-to-analog converter (CDAC). With these techniques, we can implement a 12b SAR ADC with a 10b capacitor array digital-to-analog converter (DAC). To enhance the accuracy of the ADC, a single-to-differential converted DAC is exploited with the dual sampling technique during top-plate sampling. Simulation results show that the proposed ADC can achieve a signal-to-noise plus distortion ratio (SNDR) of 70.8dB, a spurious free dynamic range (SFDR) of 83.3dB and an effective number of bits (ENOB) of 11.5b with bipolar CMOS LDMOD (BCDMOS) $0.35{\mu}m$ technology. Total power consumption is 115uW under a supply voltage of 3.3V at a sampling frequency of 1.25MHz. And the figure of merit (FoM) is 32.68fJ/conversion-step.

• Journal of Korea Multimedia Society
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• v.23 no.8
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• pp.1040-1048
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• 2020

In this study, in order to improve the implantable bone conduction transducer of the prototype proposed by Shin et al., the effect of the element parameters of the transducer on the frequency characteristics was analyzed using electromagnetic and mechanical vibration analysis. Electromagnetic analysis was performed on the size of the permanent magnet and the distance between the metal plate and the coil to derive an optimal structure that generates the maximum Lorentz force. In addition, mechanical vibration analysis was performed on the cantilever structure of the vibrational membrane in order to minimize the distortion of the transducer and to have a frequency characteristic suitable for conductive hearing loss compensation. The frequency characteristics of the transducer of the optimal structure derived through finite element method were compared with the simulation results of the previous transducer. As a result, the output magnitude (displacement) of the transducer designed with the optimal structure generated an average 8.8 times higher than the previous transducer, and the resonance frequency was generated at 0.9 kHz.

• The Transactions of the Korean Institute of Power Electronics
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• v.3 no.2
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• pp.156-164
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• 1998

The operation regions of a three-phase(3Ø) voltage-source(VS) PWM converter are classified in the current vector plane of the synchronous reference frame and their characteristics are explained. In the the power-factor decreasing region, the current control with unity power-factor can not give satisfactory performance to the given load because of the distortion of input current and the ripples and the steady-state errors in DC link voltage. In this paper, the derivation of the optimal current vector is proposed to solve these problems. With this, the input current can be controlled sinusoidally with available maximum power factor and the DC link voltage be the given load, resulting the expansion of the operation region of the 3Ø VS PWM converter. The validity of the proposed control method is proved by the experimental results.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.18 no.7
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• pp.723-730
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• 2007

This paper shows how the ACLR of power amplifier can be reduced by using Anti-phase IMD linearization technique which generate anti-phase IMD in the driver stage compare to output stage's IMD. And design process proposed. From the experimental result of W-CDMA 4FA input signal, this amplifier has ACLR -55 dBc@5 MHz offset at 30 watts average power. Compare to optimum matching technique to get maximum power gain, this technique has been improved ACLR by 12 dBc. Also this amplifier meets 50 watts average output power amplifier specification in domestic market.

• Proceedings of the Acoustical Society of Korea Conference
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• 1998.06c
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• pp.351.1-355
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• 1998

Network-based real-time multimedia applications require guaranteed performances of communication service. Also according to increased bandwidth and processing performance in the future high speed networks, it is possible to make multimedia real-time applications such as distributed real-time applications including video conference, medical imaging, and video education. These applications have characteristics of stringent performance requirements in terms of delay, delay jitter and maximum loss rate. This paper proposes a new delay control for Broadband networks with FCFS queueing. The delay control provides an alternative solution to a current problem in real-time communication; traffic distortion, which makes it difficult to meet such real-time requirements. In simulations, it shows that the proposed delay control can guarantee local and end-to-end delay.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.14 no.10
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• pp.2207-2214
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• 2010

Underwater acoustic(UWA) communication has multipath error because of reflection by sea-level and sea-bottom. The multipath of UWA channel causes signal distortion and error floor. In this paper, we proposed split input bits of channel decoder using method of maximum value, average value, LLR value for optimal estimation. Channel coding method is LDPC(N size=16000) standard in DVB-S2. As shown in simulation results, the performance of LLR value method is better than other methods.