• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.20 no.2
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• pp.195-200
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• 2020

Leakage and Bragg condition of optical waveguides with blazed grating profile are evaluated in detail by using novel and rigorous modal transmission-line theory (MTLT) based on eigenvalue problem. The blazed waveguides classified as symmetric, sawtooth and asymmetric gratings occur leaky-wave stop-band at Bragg conditions and anomalies based on Rayleigh condition near Bragg conditions. Furthermore, DFB properties of blazed waveguides at Bragg conditions are analyzed by applying longitudinal equivalent transmission-line with characteristic impedance of periodic grating. The numerical results show that the reflected power of DFB waveguides is maximized at Bragg conditions in which leaky-wave stop-bands occur.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.35D no.10
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• pp.1-6
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• 1998

The dielectric effects of plastic packages on GaAs($\varepsilon$$_{r}$=13) MMIC microstrip characteristics are analyzed using the spectral domain method (SDM). As being packaged by typical FR-4 composites ($\varepsilon$$_{r}$=14.2) for PCB substrates and plastic packages, the characteristic impedance is reduced by about 6 %, but the effective dielectric constant is increased by 13 % from those of bare microstrip, respectively. The parasitic effects of the packaging materials can greatly degrade the performance of the packaged MMIC. We also calculated the optimum microstrip width, which maintains the 50 $\Omega$ matching condition after plastic packaging. These calculated results can be used to optimize the plastic packages, and extend the application ranges for low cost MMIC production.n.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.7 no.2
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• pp.43-49
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• 2008

In this paper, new directional couplers for T/R switch of UHF RFID applications are proposed to overcome TX-to-RX leakage problem. The proposed method can remove TX-to-RX leakage caused by both imperfect isolation characteristic of the conventional directional coupler and the mismatch of antenna impedance. Two directional couplers are implemented using distributed elements and lumped elements respectively for the verification. The varactor tuneable circuits for compensation of the antenna mismatch is also proposed. The measurement result shows excellent TX-to-RX leakage suppression, more than 45dB in 910MHz.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.10 no.5
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• pp.71-78
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• 2011

In this paper, we describe the design and implementation of a high efficiency and broad-band Class-J mode power amplifier using gallium nitride(GaN) high-electron mobility transistor(HEMT). The matching circuit of proposed class-J mode power amplifier for 2nd harmonic impedance designed to provide pure reactance alone. The measurement results show that output power of $40{\pm}1$ dBm, power-added efficiency of 50%, and drain efficiency of 60% for a continuous wave signal at 1.4 to 2.6 GHz.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.38 no.5
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• pp.16-22
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• 2001

A novel microstrip circular slot antenna fed by a spiral line is presented in this paper. This antenna is a planar equivalent structure of an eccentric spiral antenna generates a circularly-polarized wave. We have investigated the input impedance and radiation characteristics of this antenna by using an EM (electromagnetic) simulator, and obtained a design method [or optimum structure. The main characteristic of the antenna is that the main beam direction is off-normal to the antenna plane and moves linearly into ${\theta }$ and ${\phi }$ direction as the frequency increases. This feature allows one to predict the main beam direction easily for a given operating frequency. This antenna has axial ratio lower than 3 dB in the direction of main beam over one octave bandwidth.

• Proceedings of the Korea Electromagnetic Engineering Society Conference
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• 2003.11a
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• pp.288-293
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• 2003

In this paper, Filter could use to IMT2000 repeater using resonator of Comb-line form that has waveguide structure and designed. Coupled resonators designed using slot in wall between resonators to compact. 5-stage resonators have equal structure and input and output part was optimized to get into minimum impedance. Band pass filter characteristic satisfied design condition as result that used Chebyshev function that have 0.2 dB ripple and analyze using simulation tool.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.12 no.5
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• pp.795-801
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• 2001

A method of miniaturizing branch line coupler is presented. The method utilizes the microstrip line with overlay(or superstrate). The frequency dependent characteristics, dispersion and characteristic impedance, of this line are obtained by Immitance method in spectral domain and Method of Line. The relevant spectral domain Green's function is given and used to obtain numerical results. The branch line couplers with overlays are designed and fabricated at 2 GHz. The experimental results show that the size of coupler with overlay(${epsilon}_r$=10.2) is 31.4 precent smaller than conventional coupler. This minimized coupler is suitable for Butler Matrix as feeder for mobile communication beam forming antenna.

• Journal of Advanced Navigation Technology
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• v.10 no.4
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• pp.326-332
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• 2006

In this study, the antenna was proposed for the omni-directional characteristic in horizontal plane. Therefore we proposed $1{\times}4$ microstrip patch array on cylindrical surface for studying microstrip patch antennas. This antenna is designed for 2.45GHz ISM band and applications. This antenna can be applied to the base station of wireless microphone and access point of wireless LAN. The length and width of the patch antenna and the width of the feed line were calculated by using the theory of microstrip patch antenna, by using the both the 2.5D and 3D EM simulators the optimized antenna characteristics are obtained. From result of measured, antenna's impedance of coaxial waveguide port was 51.915-j3.688 ${\Omega}$, the return loss was -31dB and VSWR was 1.081.

• The Transactions of the Korean Institute of Power Electronics
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• v.22 no.4
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• pp.330-335
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• 2017

Increased fossil fuel consumption causes global warming, environmental pollution, and abnormal climate change. Wind-generated power installation is proposed to solve this problem. Recently, the wind power plant construction case encourages the installation of the energy storage system (ESS) to improve the intermittency of wind power. The maximized ESS operation profits connected to wind power are not generated in the simplest operation pattern of charging at night and discharging at day. The battery charging efficiency improvement should be considered to get more profits. Thus, there is a possibility of increasing ESS operation profits by analyzing the battery AC and DC charging/discharging efficiency and the yearly average sealed maintenance free (SMP) in hours. In this paper, the battery impedance characteristic, AC and DC charging/discharging efficiency, and the yearly average SMP are analyzed. The operation scenario to improve the ESS battery charging efficiency connected to wind power is proposed and verified via simulation.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.19 no.9
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• pp.1782-1792
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• 1994

Ti : $LiNbO_3$ traveling-wave phase optical modulators at wavelength 1.3㎛ have been designed and fabricated, focusing on the optical waveguide and asymmetric coplanar electrode structure. To improve the phase-mismatch of traveling-wave ACPS electrode, the characteristic impedance, effective microwave index, and electrode loss have been presented as a function of geometric parameters including electrode and buffer layer thickness. Low-loss channel optical waveguides on $LiNbO_3$ were fabricated by the Ti diffusion method with $O_2$ water-vapor environment. $2.5{\mu}m$ thick electrode was successfully fabricated by double-spin image reversal process. Modulation bandwidth was limited by a resonance at 2.9 GHz and modulation bandwidth up to 2.5GHz was approxirnately measured.