• The Transactions of the Korean Institute of Electrical Engineers C
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• v.53 no.5
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• pp.273-278
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• 2004

This paper analyzed the phase noise characteristics of frequency-shifting module by figuring out the relationship between the phase noise components of 1st and 2nd local oscillator composing the frequency-shifting module and those of RF output signals shifted in frequency. Also, frequency-shifting module with the improvement of the phase noise performance was designed and implemented by means that the phase noise components of 1st local oscillator were cancelled in the output signal. Output signal has been affected by only phase noise of 2nd local oscillator, which had excellent phase noise performance than that of the 1st local oscillator.

• Journal of Power Electronics
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• v.16 no.6
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• pp.2119-2128
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• 2016

Due to detection and control errors, some high-frequency harmonics with voltage-source characteristics cause circulating currents in modular inverters. Moreover, the circulating currents are usually affected by the output filters (OF) of each module due to their filter and resonance properties. The interaction among the circulating currents in the modules increase the power loss and reduce system stability and control precision. Therefore, this paper reports the results of a study on the SPWM high-frequency harmonics circulating currents for a double-module VSI. In the paper, an analysis of the circulating-current circuits is briefly described. Next, a mathematic model of the single-module output voltage based on the carrier frequency of SPWM is built. On this basis, through mathematic modeling of high-frequency harmonic circulating currents, the formation mechanism and distribution characteristics of circular currents and their influences are studied in detail. Finally, the influences of the OF on the circulating currents are studied by mainly taking an LC-type filter as an example. A theoretical analysis and experimental results demonstrate some important characteristics. First, the carrier phase shifting of the SPWM for each module is the major cause of the SPWM harmonic circulating currents, and the circulating currents are in an odd distribution around n-times the carrier frequency $n{\omega}_s$, where n = 1, 2, 3, ${\ldots}$. Second, the harmonic circular currents do not flow into the parallel system. Third, the OF can effectively suppress the non-circulating part of the high-frequency harmonic currents but is ineffective for the circulation part, and actually reduces system stability.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.17 no.4
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• pp.8-12
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• 2003

Characteristics of optical transceiver module in radio frequency(RF) band were investigated with TO-can packaged Fabry-Perot laser diode(FP-LD). R-L-C parameters for equivalent circuit model of the LD were extracted with an impedance analyzer. With this model, impedance matching to the packaged LD could be performed by eliminating inductive components of the leads in the package by using lumped chip capacitors that have opposite reactance, while it shows resonance dip in low frequency band. The resonance dip could be removed using lumped elements for impedance matching by shifting the resonance frequency to the region out of interest.

• Journal of Biosystems Engineering
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• v.25 no.5
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• pp.351-358
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• 2000

This study was conducted to develop a speed control system of a DC motor which drove a barley seeder mounted on a combine harvester. Barley seeder mounted on a combine has been known to reduce labor and cost of barley cultivation. However, development of the seeder has been unsuccessful because the combine, a dedicated rice and barley harvester has not enough space and proper power take-off for barley seeder. To develop a barley seeder, small powered motor speed controller was required. A proximity sensor for detecting working speed of the combine and a programmable one board microprocessor was used to develope a control system. Motor parameters and motor constant, relationship between seeding rate, motor speed, groove volumes of a tested roller, torque were measured. The proximity sensor sent a frequency signal to the microprocessor. In laboratory experiments, the excitation voltage of the motor was shown not to be proportional to the size of pulse width (duty ratio). A table transforming frequency signal, that represented for working speed to proper pulse width was developed from seeding rate experiments. However, seeding rate at low frequency signal was not proportional to the working speed. Seeding rate control proportional to the frequency signal was achieved by shifting of the frequency signal.

• ETRI Journal
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• v.35 no.3
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• pp.378-385
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• 2013

An S-band multifunction chip with a simple interface for an active phased array base station antenna for next-generation mobile communications is designed and fabricated using commercial 0.5-${\mu}m$ GaAs pHEMT technology. To reduce the cost of the module assembly and to reduce the number of chip interfaces for a compact transmit/receive module, a digital serial-to-parallel converter and an active bias circuit are integrated into the designed chip. The chip can be controlled and driven using only five interfaces. With 6-bit phase shifting and 6-bit attenuation, it provides a wideband performance employing a shunt-feedback technique for amplifiers. With a compact size of 16 $mm^2$ ($4mm{\times}4mm$), the proposed chip exhibits a gain of 26 dB, a P1dB of 12 dBm, and a noise figure of 3.5 dB over a wide frequency range of 1.8 GHz to 3.2 GHz.

• Journal of the Korean Solar Energy Society
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• v.36 no.5
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• pp.19-30
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• 2016

In this study, realize voltage regulation $220Vac{\pm}10%$ or less, frequency fluctuation $60Hz{\pm}1%$ or less over the independent operation and grid-connected operation technologies for power stabilization relates to the ESS designed and manufactured in conjunction with solar installations and solar to compensate the output reduction due to the polarization of the solar module through the polarization prevention technology for preventing the optical module efficiency is lowered, in conjunction with the BMS inverter efficiency was more than 92%, more than 90% of the charging efficiency to the target. This study was designed in conjunction with the ESS solar power plants, grid-connected operation and independent operation, Peak-Cut, it can stabilize the grid via the Peak-Shifting operation

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.25 no.5
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• pp.504-514
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• 2014

An MMIC multi-function chip with a low DC power consumption for an X-band active phased array radar system has been designed and fabricated using a 0.5 ${\mu}m$ GaAs p-HEMT commercial process. The multi-function chip provides several functions: 6-bit phase shifting, 6-bit attenuation, transmit/receive switching, and signal amplification. The fabricated multi-function chip with a compact size of $16mm^2(4mm{\times}4mm)$ exhibits a gain of 10 dB and a P1dB of 14 dBm from 7 GHz to 11 GHz with a DC low power consumption of only 0.6 W. The RMS(Root Mean Square) errors for the 64 states of the 6-bit phase shift and attenuation were measured to $3^{\circ}$ and 0.6 dB, respectively over the frequency.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.25 no.3
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• pp.257-266
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• 2007

The research on red tide is generally in progress through field work, such as the naked eye and sampling. It was difficult to forecast exactly the course, from appearance of red tide to disappearance. with the established ways of investigation and analysis. Accordingly it is need to analyze environmental factors in time and space, the appearance of red tide and the path of its migration by more objective and scientific methods. In this study, GIS is applied to analyse the space character of red tide and the interpolation of IDW(Inverse Distance Weight) is applied to assume the density distribution of red tide after gather data by using Arc/Info. After IDW interpolation, the sea area occurred over 1,000 cells/ml of red tide density is extracted with CON and SUM Function of Grid Module, and the density of the sea area is accumulated daily. As a result of this study, the distribution condition of red tide is found timely and spacially by applying GIS to the sea area of red tide, the results indicated that the spatial density and the cumulative frequency about the origin of red tide using GIS, the sea area demonstrated that the maximum density and the maximum frequency varied significantly over the Nammyun of Namhae-Is. with the maximum frequency being 49 times. accordingly if data about the areas of red tide will occur from the present are accumulated, the shifting route of red tide occurrence and extinction can be predicted.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.22 no.6
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• pp.613-624
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• 2011

An MMIC multi-function chip for an X-band active phased array radar system has been designed and fabricated using a 0.5 ${\mu}m$ GaAs p-HEMT commercial process. A digital serial-to-parallel converter is included in this chip in order to reduce the number of the control interface. The multi-function chip provides several functions: 6-bit phase shifting, 6-bit attenuation, transmit/receive switching, and signal amplification. The fabricated multi-function chip with a relative compact size of 24 $mm^2$(6 mm${\times}$4 mm) exhibits a transmit/receive gain of 24/15 dB and a P1dB of 21 dBm from 8.5 GHz to 10.5 GHz. The RMS errors for the 64 states of the 6-bit phase shift and attenuation were measured to $7^{\circ}$ and 0.3 dB, respectively over the frequency.