• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.10
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• pp.590-597
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• 2018

Recently, the installation of PV systems has been increasing due to the worldwide interest in eco-friendly and renewable solar energy. On the other hand, the output power of PV systems is influenced strongly by the surrounding weather conditions. In addition, the entire operation efficiency of PV systems may be decreased considerably even if only some of the PV modules are in the shade. In other words, the existing control method at which strings with modules in series are connected to an inverter may be not operated in the case that the string voltage in partial shade is lower than the operating range of the grid connected inverter. To overcome these problems, this paper proposes an operation efficiency improvement device of a PV system using a Li-ion battery, which can compensate for the voltage of each string in the PV system when it is partially shaded. In addition, this paper presents the modeling of the operation efficiency improvement device, including PV strings, Li-ion battery and a 3-Phase grid inverter based on the PSIM S/W. From the simulation results, it was confirmed that the proposed control method can improve the operating efficiency of PV systems by compensating for the string voltage with partial shade.

• Journal of the Korea Society of Computer and Information
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• v.17 no.12
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• pp.31-39
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• 2012

In this paper, we propose a microprocessor-based automatic voltage regulator(AVR) to reduce consumers' electric energy consumption and to help controlling peak demanding power. Hybrid Switching Automatic Voltage Regulator (HS-AVR) consist of a toroidal core, several tap control switches, display and command control parts. The coil forms an autotransformer which has a serial main winding and four parallel auxiliary windings. It controls the output voltage by changing the combination of the coils and the switches. Relays are adopted as the link switches of the coils to minimize the loss. To make connecting and disconnecting time accurate, relays of the circuit have parallel TRIACs. A software phase locked loop(PLL) has been used to synchronize the timings of the switches to the voltage waveform. The software PLL informs the input voltage zero-crossing and positive/negative peak timing. The traditional voltage transformers and AVRs have a disadvantage of having a large mandatory capacity to accommodate maximum inrush current to avoid the switch contact damage. But we propose a suitable AVR for every purpose in smart grid with reduced size and increased efficiency.

• Journal of the Korean Society of Marine Environment & Safety
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• v.27 no.7
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• pp.1124-1128
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• 2021

As regulations of emissions from ships become more stringent, electric propulsion systems have been increasingly used to solve this problem in vessels ranging from large merchant ships to small and medium-sized ships. Methods for improving the efficiency of the electric propulsion system include the improvement of power sources; the use of a system linked to environmentally friendly power sources, such as batteries, fuel cells, and solar power; and the development of hardware and control methodology for rectifiers, power conversion devices, and propulsion motors. The method using a phase-shifting transformer with diodes has been widely used for rectification. Power semiconductor devices with grid connection to an environmentally friendly power source using DC distribution, a variable speed power source, and the application of small and medium-sized electric propulsion systems have been developed. Accordingly, the demand for active front-end (AFE) rectifiers is increasing. In this study, a method using a neural network rather than a conventional proportional-integral controller was proposed to control the AFE rectifier. Tested controller data were used to design a neural network controller trained through MATLAB/Simulink. The neural network controller was applied to a rectification system designed using PSIM software. The results indicated the effectiveness of improving the waveform and power factor DC output stage according to the load variation. The proposed system can be applied as a rectification system for small and medium-sized environmentally friendly ships.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.42 no.2 s.332
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• pp.23-30
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• 2005

This paper describes a DLL(delay locked loop)-based multi-clock generator having the lower active stand-by power as well as a fast relocking after re-activating the DLL. for low power and high speed VLSI chip. It enables a frequency multiplication using frequency multiplier scheme and produces output clocks with 50:50 duty-ratio regardless of the duty-ratio of system clock. Also, digital control scheme using DAC enables a fast relocking operation after exiting a standby-mode of the clock system which was obtained by storing analog locking information as digital codes in a register block. Also, for a clock multiplication, it has a feed-forward duty correction scheme using multiphase and phase mixing corrects a duty-error of system clock without requiring additional time. In this paper, the proposed DLL-based multi-clock generator can provides a synchronous clock to an external clock for I/O data communications and multiple clocks of slow and high speed operations for various IPs. The proposed DLL-based multi-clock generator was designed by the area of $1796{\mu}m\times654{\mu}m$ using $0.35-{\mu}m$ CMOS process and has $75MHz\~550MHz$ lock-range and maximum multiplication frequency of 800 MHz below 20psec static skew at 2.3v supply voltage.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.28 no.10
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• pp.769-778
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• 2017

In this paper, a self-interference signal cancellation(SIC) circult for In-band Full-Duplex has been developed and tested in RF/analog region. By use of this SIC circuit, a FM two-way radio has been developed working at FRS(Family Radio Service) band. The two-way radio device is transmitting the FM modulated signal and demodulating the wanted FM signal at the same time. A circulator is used to enable a single antenna to transmit and receive simuultaenously. The receiver circuit needs to cancel out the self-interference signal due to the transmit signal. A vector modulator(VM) is used to control the phase and magnitude of the esitmated signal. And in-phase and quadrature correlators are used to figure out the optimal coefficients of the VM to remove the self-interference signal according to the change of channel environment. In this work, SA58646 has been used as the FM transceiver, and the system is tested with a frequency of 465 MHz and a bandwidth of 12.5 kHz FM signal. The output power is 17.2 dBm at the antenna port, and the self intererence signal level is measured -49.2 dBm at the receiver end. Therefore the SIC level is measured by 66.4 dB.

• Advances in aircraft and spacecraft science
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• v.5 no.2
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• pp.225-237
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• 2018

The difficulties of satellite vibration testing are due to the commonly expressed qualification requirements being incompatible with the limited performance of the entire controlled system (satellite + interface + shaker + controller). Two features cause the problem: firstly, the main satellite modes (i.e., the first structural mode and the high and low tank modes) are very weakly damped; secondly, the controller is just too basic to achieve the expected performance in such cases. The combination of these two issues results in oscillations around the notching levels and high amplitude beating immediately after the mode. The beating overshoots are a major risk source because they can result in the test being aborted if the qualification upper limit is exceeded. Although the abort is, in itself, a safety measure protecting the tested satellite, it increases the risk of structural fatigue, firstly because the abort threshold has been already reached, and secondly, because the test must restart at the same close-resonance frequency and remain there until the qualification level is reached and the sweep frequency can continue. The beat minimum relates only to small successive frequency ranges in which the qualification level is not reached. Although they are less problematic because they do not cause an inadvertent test shutdown, such situations inevitably result in waiver requests from the client. A controlled-system analysis indicates an operating principle that cannot provide sufficient stability: the drive calculation (which controls the process) simply multiplies the frequency reference (usually called cola) and a function of the following setpoint, the ratio between the amplitude already reached and the previous setpoint, and the compression factor. This function value changes at each cola interval, but it never takes into account the sensor signal phase. Because of these limitations, we firstly examined whether it was possible to empirically determine, using a series of tests with a very simple dummy, a controller setting process that significantly improves the results. As the attempt failed, we have performed simulations seeking an optimum adjustment by finding the Least Mean Square of the difference between the reference and response signal. The simulations showed a significant improvement during the notch beat and a small reduction in the beat amplitude. However, the small improvement in this process was not useful because it highlighted the need to change the reference at each cola interval, sometimes with instructions almost twice the qualification level. Another uncertainty regarding the consequences of such an approach involves the impact of differences between the estimated model (used in the simulation) and the actual system. As limitations in the current controller were identified in different approaches, we considered the feasibility of a new controller that takes into account an estimated single-input multi-output (SIMO) model. Its parameters were estimated from a very low-level throughput. Against this backdrop, we analyzed the feasibility of an LQG control in cancelling beating, and this article highlights the relevance of such an approach.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.48 no.3
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• pp.34-41
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• 2011

This paper presents a wide tuning range, fine-resolution DCO (Digitally Controlled Oscillator) with an active inductor. In order to control the frequency of the DCO, the transconductance of the active inductor is tuned digitally. In addition, the DCO gain needs to be calibrated digitally to compensate for gain variations. To cover the wide tuning range, an automatic three-step coarse tuning scheme is proposed. The DCO total frequency tuning range is 1.4 GHz (2.1 GHz to 3.5 GHz), it is 58 % at 2.4 GHz. An effective frequency resolution is 0.14 kHz/LSB. The proposed DCO is implemented in 0.13 ${\mu}m$ CMOS process. The total power consumption is 6.6 mW from a 1.2 V supply voltage. The phase noise of the DCO output at 2.4 GHz is -120.67 dBc/Hz at 1 MHz offset.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.39 no.5
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• pp.8-15
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• 2002

We optimally designed the VCO(voltage-controlled oscillator) with spiral inductor using the MOSIS HP 0.5${\mu}{\textrm}{m}$ CMOS process. With the developed SPICE model of spiral inductor, the quality factor of spiral inductor was maximized at the operating frequency by varying the layout parameters, e.g., metal width, number of turns, radius, space of the metal lines. For the operation frequency of 2㎓, the inductance of about 3nH, and the MOSIS HP 0.5 CMOS process with the metal thickness of 0.8${\mu}{\textrm}{m}$, oxide thickness of 3${\mu}{\textrm}{m}$, the optimal width of metal lines is about 20${\mu}{\textrm}{m}$ for the maximum Quality factor. With the optimized spiral inductor, the VCO with LC tuning tank was designed, fabricated and measured. The measurements were peformed on-wafer using the HP8593E spectrum analyzer. The oscillation frequency was about 1.610Hz, the frequency variation of 250MHz(15%) with control voltage of 0V - 2V, and the phase noise of -108.4㏈c(@600KHz) from output spectrum.

• Journal of the Institute of Electronics and Information Engineers
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• v.51 no.7
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• pp.26-36
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• 2014

The needs of active phased arrays antenna system is getting more increased for IMT-Advanced system efficiency. The active phased array structure consists of lots of small transceivers and radiation elements to increase system efficiency. The minimized module of high efficiency transceiver is key for system implementation. The power amplifier of transmitter decides efficiency of base-station. In this paper, we design and implement minimized module of high efficiency transceiver for IMT-Advanced active phased array system. The temperature compensation circuit of transceiver reduces gain error and the analog pre-distorter of linearizer reduces implemented size. For minimal size and high efficiency, the implented power amplifier consist of GaN MMIC Doherty structure. The size of implemented module is $40mm{\times}90mm{\times}50mm$ and output power is 47.65 dBm at LTE band 7. The efficiency of power amplifier is 40.7% efficiency and ACLR compensation of linearizer is above 12dB at operating power level, 37dBm. The noise figure of transceiver is under 1.28 dB and amplitude error and phase error on 6 bit control is 0.38 dB and 2.77 degree respectively.

• Journal of the Korean Graphic Arts Communication Society
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• v.30 no.3
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• pp.89-114
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• 2012

For as to world, the concern about the environment problem is enhanced than any other time in the past because of being 21 century. And the environment problem is highlighted as the world-wide issue. The time of the environment problem intimidates the alive of the mankind and presence of an earth over the time. It becomes the essentiality not being selection in the personal living or the economical viewpoint now to prepare for the climatic modification. As to the company management, the green growth period which it excludes the environment management considering an environment, cannot carry on the company the continued management comes. That is, in the change center of the management paradigm, there is the environment management. Nearly, the greenhouse gas which the publication industry is the environmental toxic material like all industries is generated. The greenhouse gas is ejected in the process of running the manufacturing process and print shop of the various kinds material used as the raw material of the book. Particularly, the tree felling for getting the material of the paper is known to reach the direct influence on the global warming. This study does according to an object it considers and organizes the environment parameter based on this kind of fact as to the publication industry. And it is determined as the reference which is used as the basic materials preparing the case that carbon exhaust right transaction(CAP and TRADE) drawing are enforced in all industries and is sustainable the management of the publication industry and reduces the environmental risk among the company many risk management elements and plans and enforces the publication related policy that there is a value. In the printing publication industry, this study tried to inquire into elements discharging the environmental pollutant or the greenhouse gas. Additionally, in the printed publication production process, it tried to inquire into the effort for an environment-friendly and necessity at the printing paper and the printers ink, regarded as the element discharging the greenhouse gas all kinds of the printing materials, operation of the print shop and all kinds of the machines and recycle process, and etc. These considerations make these industrial field employees aware of the significance about a conservation and environmental protection. They try to give a help in the subsequent study producing quantitatively each environmental parameter emission of green house gas. This makes the calculation of the relative $CO_2$ output reproached ultimately possible. Meanwhile, in a sense, many research protects and improving an environment in connection with the contents of research at the printing publication industrial field is in progress. There will be the voluntary human face that it has to protect an environment but this can not do by the outside factor according to all kinds of environment related law and regulation. Anyway, because of acting on company management as the factor of oppression, the increase of this environment-related correspondence cost could know that the research that the environment loading relates with a procurement and development, environment management system introduction, quality control standard, including, normalizing including a material, and etc. through the part of the effort to reduce the cost low was actively in progress. As to the green growth era, as follows, this paper prescribed the subject and alternative of the print publication industry. It is surrounded by the firstly new digital environment and the generation of the subject. And secondly the printing industry is caused by the point of time when the green growth leaves by the topic which is largest in the global industry and it increases. The printing publication industry has to prepare the bridgehead for the environment-friendly green growth as the alternative for this resolution with first. The support blown in each industry becomes the obligation not being selection. Prestek in which the print publishing was exposed to spend many energies and which is known as the practice of the sustainable print publishing insisted that it mentioned importance of the green printing through the white pages in 2008 and a company had to be the green growth comprised through the environment-friendly activity. The core management for the sustainable printing publication industry presented from Presstack white pages is compacted to 4 words that it is a remove, reduce, recover, and recycle. Second, positively the digital printing(POD) system should be utilized. In the worldwide print out market, the digital printing area stops at the level of 10% or so but the change over and growth of the market of an analog-to-digital will increase rapidly in the future. As to the CEO Jeff Hayes of the Infoland, the offset print referred to that it of the traditional method got old and infirm with the minor phase of the new printing application like the customer to be wanted publication and the print of the digital method led the market. In conclusion, print publishers have to grasp well the market flow in the situation where a digitalization cannot be generalized and a support cannot avoid. And it keeps pace with the flow of the digital age and the recognition about the effort for the development and environment problem have to be raised. Particularly, the active green strategy is employed for the active green strategy.