• Journal of Korea Multimedia Society
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• v.12 no.7
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• pp.971-978
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• 2009

The paper is a phase controlled loop antenna for multi-media devices. We developed a phase control loop pattern arrangement methods for loop antenna in mobile devices like as a cell phone and PCS, WCDMA. In the loop antenna pattern, arrange close adhesive the loop antenna pattern $180^\circ$ cycle in wave length, the radiated electro-magnetic wave from close adhesive loop pattern become to coherent wave than the phase controlled loop antenna has high efficiency and high radiation gain. To acquire a wide band width on phase controlled loop antenna, we arrange a multiple phase controlled loop pattern that has a different length each other. Different length for each other loop pattern cause a different frequency that we can acquire a wide band width for loop antenna from close adhesive phase control. In experiment, we designed a CDMA850 mobile multi-media antenna in 20mm$\times$20mm area thickness 0.4mm, the radiation efficiency is over 60% and radiation gain is over 0dBi.

• Journal of the Korea Institute of Military Science and Technology
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• v.13 no.6
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• pp.1071-1079
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• 2010

This paper describes the design and fabrication of a high-efficiency GaN HEMT(Gallium Nitride High-electron Mobility Transistor) Pallet power amplifier module for S-band phased array radar applications. Pallet amplifier module has a series 2-cascaded power amplifier and the final amplification-stage consists of balanced GaN HEMT transistor. In order to achieve high efficiency characteristic of pallet power amplifier module, all amplifiers are designed to the switching-mode amplifier. We performed with various PRF(Pulse Repetition Frequency) of 1, 10, 100 and 1000Hz at a fixed pulse width of $100{\mu}s$. In the experimental results, the output power, gain, and drain efficiency(${\eta}_{total}$) of the Pallet power amplifier module are 300W, 33dB, and 51% at saturated output power of 2.9GHz, respectively.

• International Journal of Reliability and Applications
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• v.6 no.1
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• pp.1-12
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• 2005

A new test for testing that a life distribution is exponential against the alternative that it is harmonic new better (worse) than used in expectation upper tail HNBUET (HNWUET), but not exponential is presented based on the highly popular 'Kernel methods' of curve fitting. This new procedure is competitive with old one in the sense of Pitman's asymptotic relative efficiency, easy to compute and does not depend on the choice of either the band width or kernel. It also enjoys good power.

• Journal of Advanced Navigation Technology
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• v.16 no.1
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• pp.27-34
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• 2012

In this paper, Coplanar waveguide(CPW)-fed slot loop antenna, which is applicable to the dual band(2.4GHz~2.4835GHz, 5.15GHz~5.825GHz) for the wireless LAN, is proposed. In order to miniaturize the proposed antenna, slot loop is bent by meandering. The resonant frequencies in the required dual band are adjusted by variation of the resonant length of slot loop as well as slot width. In particular, use of capacitive coupling CPW feed provides impedance matching without a seperate matching circuit, because the amount of electromagnetic coupling can be controlled by the offset between feed and radiator. As a result, it has been observed that the proposed antenna satisfies not only the required return loss(${\leq}10dB$) but also has high efficiency(${\geq}80%$) over the whole frequency band. In order to check the validity of the proposed antenna, some simulated results for return loss and radiation pattern are presented in comparison with the measured results.

• Korean Journal of Optics and Photonics
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• v.4 no.4
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• pp.442-446
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• 1993

A flashlamp pumped Ti: sapphire laser was designed and fabricated in the laboratory. In order to find out the optimum pumping condition, three kinds of discharge circuits of which the pulse width are 10${\mu}s$, 45${\mu}s$, 65${\mu}s$ were designed. The fluorescent energy converter LD-490 of which the fluorescence spectra is coincident to the absorption band of Ti: sapphire was used to improve the laser efficiency. The laser output characteristics for three different concentrations of LD-490 and for three different pumping pulse widths were measured. As a result, the shorter the flashlamp pulse width, the higher the overall efficiency was achieved. When pumping light pulsewidth was 10${\mu}s$, the best efficiency was obtained at the concentration 1.0${\times}10^{-3}$mol/l of LD-490 dye. At lower concentrations the efficiencies were decreased.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.22 no.12
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• pp.1139-1147
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• 2011

In this paper, a design and fabrication of GaN power amplifier for the S-band frequency (400 MHz bandwidth) are presented. A combining path using ${\lambda}$/4 transmission line is implemented for GaN pallet amp. Both the combiner with suspended-type transmission structure for low-loss and the suspended stripline coupler with aperture coupling for auto gain control are realized for achieving high-power high-efficiency amplifier. Proposed power amplifier demonstrated a 5 kW peak output power, 27.8 % efficiency, 67 dB gain without ALC and a 4 kW peak output power, 25.5 % efficiency, 0.1 dB droop at 200 usec pulse width and 10 % duty with ALC.

• Journal of Ocean Engineering and Technology
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• v.28 no.5
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• pp.474-483
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• 2014

The majority of existing WECs (wave energy converters) are designed to achieve maximum power at a resonance condition. In the case of a single WEC, its size must be large enough for tuning, and it has high efficiency only within a limited frequency band. Recently, wave power extraction by deploying many small buoys in a compact array has been studied under the assumption that the buoy's size and separation distance are much smaller than the water depth, wave length, and size of the array. A boundary value problem involving the macro-scale boundary condition on the mean surface covered by an infinite strip of buoys is solved using the eigenfunction expansion method. The energy extraction efficiency (${\varepsilon}=1-R^2_f-T^2_r$), where $R_f$ and $T_r$ are the reflection and transmission coefficients for a strip array of buoys, is assessed for various combinations of packing ratio, strip width, and PTO damping coefficient.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.40 no.9
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• pp.1693-1698
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• 2015

This paper proposed a PFM(pulse-frequency modulator) boost converter which has dual pulse-width. The PFM boost converter is composed of BGR(band gap voltage reference generating circuit), voltage reference generating circuit, soft-start circuit, error amplifier, high-speed comparator, inductor current sensing circuit and pulse-width generator. Converter has different inductor peak current so it has wider load current range and smaller output voltage ripple. Proposed PFM boost converter generates 18V output voltage with input voltage of 3.7V and it has load current range of 0.1~300mA. Simulation results show 0.43% output voltage ripple at ligh load mode and 0.79% output voltage ripple at heavy load mode. Converter has efficiency 85% at light lode mode and it has maximum 86.4% at 20mA load current.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.25 no.2
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• pp.172-182
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• 2014

In this paper, is is presented the result of design and fabrication for X band T/R module using in active array radar. The high power RF circuit was fabricated using GaN element, so that high power and high efficiency was fulfilled comparing with the previous T/R module that have under 50 W output power for X band. Designed X band T/R module demonstrated 200 W(53 dBm) peak power, 20 us pulse width with 0.4 dB pulse droop and 20 % duty cycle. And it has characteristics of 26 dB receive gain and 4.5 dB noise figure. The structure was applied to prevent serious damage of receive path and GaN HPA by transmitting power during trasmit time of a pulse radar.

• Proceedings of the IEEK Conference
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• 2005.11a
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• pp.1133-1136
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• 2005

The proposed high-speed backup and recovery system is a high performance backup software based on multi streaming I/O and high speed/high compression technology, and can realize an increase efficiency of backup volume without any increase of backup H/W equipments since it provides a high performance in data backup of a user and executes high compression very fast. Particularly, it minimizes consumption of network band width through a development of algorism for high compression in connection with backup equipments in a large-scaled system environment, is automated when it is recovered due to danger and troubles, and allows users to conveniently access in various ways since GUI and CLI for execution and management are all provided.