• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.18 no.4 s.119
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• pp.416-422
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• 2007

In this paper, a broadband 2-way power divider which can be used from 20 MHz to 500 MHz in the V/UHF band is designed using transmission-line transformer and ferrite toroid. A 2:1 impedance transformer instead of the conventional 4:1 impedance transformer is realized and this 2:1 transformer is connected with the conventional bridge-type 2-way divider to form a 2-way power divider. Insertion loss of about 3.5 dB, isolation of less than -10 dB, and return loss of less than -10 dB in most band of interest are measured.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.18 no.8
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• pp.904-912
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• 2007

In this paper, a broadband 4-way power divider which can be used from 20 MHz to 500 MHz in the V/UHF band is designed using transmission-line transformer and ferrite toroid. A 4:1 impedance transformer is realized and this 4:1 transformer is connected with bridge-type 2-way dividers to form a 4-way rower divider, Insertion loss of about 6.8dB, isolation of less than -20dB, and return loss of less than -15dB in most band of interest are measured.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.11a
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• pp.504-514
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• 2003

We investigate global bifurcation in the subharmonic motion of a circular plate with one-to-one internal resonance. A system of autonomous equations are obtained from the partial differential equations governing the system by using Galerkin's procedure and the method of multiple scales. A perturbation method developed by Kovacic and Wiggins is used to find Silnikov type homoclinic orbits. The conditions under which the orbits occur are obtained.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.05a
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• pp.287-296
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• 2003

We investigate global bifurcation in the motion of an harmonically excited circular plate with one-to-one internal resonance. A perturbation method developed by Kovacic and Wiggins is used. Silnikov type homoclinic orbit has been pursued but it has turned out not to exist.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.23 no.6
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• pp.740-747
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• 2019

In this paper, an antenna applicable to WLAN and WiMAX frequency bands is designed, fabricated, and measured. The proposed antenna is designed to have two branch strip line in the patch plane and a rectangular slit in the ground plane based on microstrip feeding for triple band characteristics and added a vertical strip in the ground plane to enhance impedance bandwidth characteristics. The proposed antenna is designed on a substrate with a relative permittivity of 4.4, a thickness of 1.0 mm, and has a size of $18.0mm(W1){\times}37.3mm$ (L4+L5+L7). From the fabricated and measured results, impedance bandwidths of 480 MHz (2.32 to 2.80 GHz) for 2.4/2.5 GHz band, 810 MHz (3.22 to 4.03 GHz) for 3.5 GHz band, and 1,820 MHz (5.05 to 6.87 GHz) for 5.0 GHz band were obtained based on the impedance bandwidth. Measured 3D pattern and gains are displayed.

• The Journal of the Korea institute of electronic communication sciences
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• v.10 no.4
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• pp.441-448
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• 2015

In this paper, a CPW-fed dual-band monopole antenna with two branch strips for WLAN(Wireless Local Area Networks) applications was designed, fabricated and measured. The proposed antenna is based on a CPW-feeding structure, and composed of two branch strips and then designed and tuned the length of two branch lines to obtained required frequencies bands. To obtain the optimized parameters, we used the simulator, Ansoft's High Frequency Structure Simulator(HFSS) and carried out simulation about parameters $L_5$, $L_8$, $W_3$, $W_5$, $W_9$. The proposed antenna is fabricated on the FR-4 substrate using the obtained parameters. The numerical and experiment results demonstrated that the proposed antenna obtained the -10 dB impedance bandwidth 1,095 MHz (1.57~2.665 GHz) for 2.4 GHz band and 1,680 MHz (4.99~6.67 GHz) for 5 GHz band satisfied requirement while simultaneously covering the WLAN bands. And characteristics of gain and radiation patterns are determined for WLAN operating bands.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.20 no.6
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• pp.516-525
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• 2009

This paper described the design and fabrication of broadband 4-way $90^{\circ}$ power divider which has a $90^{\circ}$ phase difference between output ports in 20${\sim}$100 MHz VHF-band. A 4-way $90^{\circ}$ power divider was designed using 4-way in-phase power divider which consisted of three 2-way in-phase power dividers and two second-order all pass filters which gives $90^{\circ}$ phase difference between output ports. The measured insertion loss was less then 6.6 dB, return loss and isolation were better than 19 dB, and phase error between $90^{\circ}$ phase difference outputs was less than ${\pm}$1$^{\circ}$.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.16 no.7 s.98
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• pp.732-739
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• 2005

In this paper, the design and implementation of the Ka-band(20/30 GHz) waveguide diplexer with an E-plane T-junction are described. The waveguide diplexer consists of a transmit filter and a receive filter combined to the antenna port via an E-plane T-junction. The reason why the E-plane T-junction structure was selected is to reduce PIM(Passive Intermodulation) level as the split-plane is located in the low electrical current zone. The optimization was performed using the equivalent circuit so that the computation time might reduce. The structure of the diplexer was designed to handle high power and the multipaction analysis was performed. The multipaction margin was greater than 12 dB and satisfied with ESA/ESTEC recommendation. The manufactured diplexer shows minimum return loss of 22 dB, maximum insertion loss of 0.20 dB and maximum isolation of -40 dB for both transmitted receive bands. Those mean the analysis results of the waveguide diplexer were well agreed with the electrical performance test.

• The Journal of the Korea institute of electronic communication sciences
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• v.14 no.1
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• pp.119-126
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• 2019

In this paper, a monopole antenna applicable to WLAN standardization is designed, fabricated, and tested. The proposed antenna is designed to have three microstrip lines based on microstrip feeding method and inserted one stub to enhance impedance characteristics. Then, it obtained triple band characteristics of the proposed antenna. We adjusted and optimized the lengths and width of the three microstrip lines and one inserted stub to obtain the required impedance bandwidth for this paper. The proposed antenna has $23.0mm(W){\times}53.1mm(L1)$ on a dielectric substrate of $24.0mm(W1){\times}60.0mm(L){\times}1.0mm$ size. From the fabrication and measurement results, bandwidths of 158 MHz (841 to 1000 MHz) for 900 MHz band, 630 MHz (2.32 to 2.95 GHz) for 2400 MHz band, and 1,040 MHz (4.95 to 5.99 GHz) for 5000 MHz band were obtained based on the impedance bandwidth. The fabricated antenna also obtained the measured gain and radiation pattern characteristics in the required triple band of the proposed antenna.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.45-45
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• 2008

$SrTiO_3$/Organic composites 는 Inorganic/organic 복합재료로, 유전 특성이 우수하고, 저온하여 제조단가의 감소가 가능하다. 이를 바탕으로 $SrTiO_3$/Organic composites 복합재를 이용한 가능성을 확인하기 위해 Multilayer 구조의 Coupler를 설계, 제작 후 특성을 분석하였다. Coupler 는 RF signal을 분기하기 위한 목적으로 평행한 한 쌍의 Conductor line 구조를 가진다. 2개의 Line 의 길이를 특정주파수 $f_0$의 wavelength $\lambda$/4 로 설계하여 서로 근접 시켰을 때 $f_0$를 중심으로 RF 신호 분기 현상이 나타난다. 보다 넓은 대역에 걸쳐서 신호분기를 하기 위해서는 두 line 간의 간격을 좁혀 Signal coupling 효과를 증가 시킨다. single layer conductor 구조에서는 물리적인 한계가 있으므로, multilayer 구조를 사용하면 보다 넓은 대역의 Coupled line coupler 로서 기능하게 된다.