• The Journal of Korean Institute of Communications and Information Sciences
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• v.22 no.8
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• pp.1747-1754
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• 1997

The helical array antenna is designed for domestic DBS(Directcast Satellite) reception. The antenna diameter is determined 30cm with 168 element s to cover from Moojoo (beam center) to Seoul. The helical antenna with 2-turns and 4.deg. pitch angle is chosen as array elements for good axial ratio and antenna height. In array antenna design, row distance is 0.787.lambda., array distance is 0.824.lambda. in the same row. The feed is constructed using the radial waveguide to decrease the height of antenna. The measured values of the designed antenna are not only satisfied with the design goals but also similar to theoritical values except the axial ratio.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.18 no.2 s.117
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• pp.158-165
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• 2007

In this paper, the circularly polarized $4{\times}4$ array antenna is proposed for the X-band. A single antenna consists of square patch and unequal cross-aperture coupled feeding. The RHCP(Right Handed Circularly Polarization) is generated by unequal cross-aperture coupled feeding. By reducing space among elements of way antenna from 0.8 ${\lambda}_0$ to 0.45 ${\lambda}_0$, the mounting area of array antenna is miniaturized. The $2{\times}2$ array antenna is designed using sequential rotation feeding network. The good level of gain, axial ratio, and impedance bandwidth are achieved. The $4{\times}4$ array antenna is extended by ${\lambda}/4$ transformer and T-junction power divider. The simulated maximum radiation gain is 15.09 dBi at 10 GHz. The simulated 3 dB Axial Ratio bandwidth is from 9.05 to 10.4 GHz(13.5%). Also the measured impedance bandwidth($VSWR{\leq}2$) of manufactured $4{\times}4$ array antenna is from 8.45 to 11.84 GHz(33.9%). The measured maximum radiation gain is 11.10 dBi at 10 GHz. The measured 3 dB Axial Ratio bandwidth is from 9.42 to 10.47 GHz(10.5%).

• Journal of the korean Society of Automotive Engineers
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• v.5 no.1
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• pp.24-31
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• 1983

혼합기 어큐물레이터를 부착시킨 연소실에 관한 새로운 아이디어를 고찰하였다. "혼합기어큐물 레이터실 (Mixture Accumulator Chamber; MA Chamber)"로 명명한 이 연소실은 점화전 압축 행정중에 부하상태와 관계없이 내부의 가한 기체난류를 일으킬 수 있다. 이러한 기관(MA engine)의 성능과 그 특성을 연구하였다. 그 기관의 베이스기관(base engine)에 비하여 기관압 축비를 증가시킬 수 있고 희박혼합기로서 안정연소를 시킬 수 있음이 확실하다. 있음이 확실하다.

• Proceedings of the KAIS Fall Conference
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• 2006.05a
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• pp.384-387
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• 2006

본 논문에서는 GPS용 Compact Truncated 패치 안테나를 제작 및 설계하였다. 또한 각모서리에 슬롯을 이용하여 소형화를 유도하였다. 중심주파수는 1.575GHz를 사용하였으며, 제작된 안테나는 VSWR 2:1 이하에서 약 50MHz의 대역폭을 보였으며, 1.575MHz에서 축비 2.7dB인 결과를 얻었다.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.23 no.3
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• pp.292-299
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• 2012

This paper proposes the design of circularly polarized multi band antenna for a non-linear junction detector (NLJD) system. In order to design for broad bandwidth, the CPW (Co-Planar Waveguide) feeding method is considered in this design. In order to realize the circular polarization, the axial ratio was controlled by inserting a $45^{\circ}$ inclined slot on radiating element and by cutting an edge of the radiating patch. Measurement results of return loss, bandwidth, axial ratio, polarization pattern and gain are agreed well with their simulation results in interested frequency band at 2.4~ 2.44 GHz, 4.84~4.92 GHz, and 7.28~7.32 GHz.

• Journal of the Korean Ceramic Society
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• v.39 no.3
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• pp.308-314
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• 2002

The nanocrystalline zirconia powder was synthesized from the zirconium hydroxide precipitate by hydrothermal process with the reaction temperature range 100∼250$^{\circ}$C, reaction time 1∼48 hours and additive concentration 1, 5 N NaOH solutions. The lower hydrothermal treatment temperature, the inner spherical tetragonal zirconia was synthesized. The fraction of monoclinic phase zirconia with rod shape increased with increasing the hydrothermal treatment temperature. As the concentration of the NaOH solution increases, the synthesized particle in breadth and length increased; breadth and length ratio decreased. In the case of the low concentration of NaOH solution, however, the particle length became relatively larger than its breadth resulting in the rod-shaped particles with bigger aspect ratio.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.20 no.8
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• pp.806-812
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• 2009

In this paper, the omnidirectional circularly polarized(CP) antenna using arc-shaped mushroom structure with curved branch is proposed. To obtain a vertical polarization and an omnidirectional radiation pattern, the CP antenna uses zeroth-order resonance(ZOR) mode of composite right and left handed(CRLH) transmission line. The horizontal polarization is achieved by the curved branches. Also, the spacing between curved branch and arc-shaped mushroom structure gives the $90^{\circ}$ phase difference between vortical and horizontal polarization. The proposed antenna, therefore, has an omnidirectional CP radiation pattern In the azimuthal plane. The electrical size of the proposed antenna is reduced by 38%, compared with that of the previously presented omnidirectional CP antenna. In addition, the CP antenna is simply designed without $90^{\circ}$ phase shifter and dual feed line. The proposed antenna uses a Bazooka balun for good impedance matching and radiation pattern. To improve 3 dB axial ratio in XY plane, the designed antenna is optimized. After optimization, the measured 3 dB axial ratio in XY plane is observed in $86{\sim}282^{\circ}$.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.17 no.5
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• pp.128-134
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• 2018

In this paper, two ports feeding a microstrip patch antenna using a quadrature hybrid circuit was proposed to enhance the bandwidth for the global positioning system(GPS). The square patch was designed, and the probe feeding was applied. The quadrature hybrid chip circuit for two-port feeding was designed, and output ports that have a 90-degree phase difference feed to the patch antenna. The designed patch and quadrature hybrid circuit were implemented on an FR4 board, and were combined. The measurement of the bandwidth within a voltage standing wave ratio(VSWR) of 2:1 and axial ratio(AR) in 3dB were wide band as 29% BW (1,230~1,700 MHz) and 15.87% BW (1,400~1,650 MHz), respectively. Antenna gain were measured 2.75dBi at the center frequency.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.15 no.12 s.91
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• pp.1178-1183
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• 2004

In this paper, a novel microstrip patch antenna with switchable polarization is proposed. The proposed antenna has a simple structure, consisting of a square radiating patch, a pair of L-type spur-lines, and a microstrip line feed. It can produce either linear polarization or circular polarization by setting the diode on or off From the measured results, low cross polarization levels when operated in the linear polarization, and good axial ratios in the circular state have been observed.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.17 no.1 s.104
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• pp.60-66
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• 2006

In this paper, a circular microstrip patch antenna for switchable polarization is presented. For the switchable polarization, pairs of tuning stubs and two PIN diodes are utilized. By independently setting the PIN diodes on or off, the antenna produces either linear polarization or circular polarization. From the results, the -10 dB impedance bandwidths of 57.0 MHz($2.4\%$) and 50.0 MHz($2.1\%$) when operated in the linear polarization, and the 3 dB axial ratio bandwidth of $1.3\%$ with minimum of 0.2 and 0.9 dB in the circular polarization have been observed.