• Journal of the Korean Institute of Telematics and Electronics A
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• v.32A no.8
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• pp.153-165
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• 1995

The design procedure of a GaAs/AlGaAs semiconductor matrix optical switch is presented for a simplified tree architecture in the viewpoint of optical loss. A low loss, 0.537 dB/cm, pin type substrate is designed by considering the loss due to imputity doping at 1.3 $\mu$m wavelength. The operating voltage and the device length of a reversed ${\Delta}{\beta}$ electro-optic directional coupler(EODC) swith which is a cross-point device of the 4${\times}$4 matrix optical switch and the bending loss of rib waveguide are caculated as functions of waveguide parameters and bending parameters. There is an optimum bending radius for some waveguide parameters. It is recommened that higher optical confinement conditions such as wide waveguide width and higher rib-height should be chosen for structural parameters of a low loss and a process insensitive 4${\times}$4 matris optical switch. A 4${\times}$4 optical matrix switch which has a 3 dB loss and a 12 volt operating voltage is designed.

• Journal of the Korean Society for Railway
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• v.19 no.4
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• pp.468-479
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• 2016

In order to supply power to online monitoring systems that are attached to high voltage catenary or overhead wires, a wireless power transfer system is required that is able to transmit power over the insulation gap. Such wireless power transfer systems have transmitter and receiver coils that have diameters of over 10cm. This paper focused on an investigation of the sources of loss in the coils when the coils are fabricated using printed circuit board technology. Using finite element simulation results, it has been shown that the dielectric loss in the substrate was the dominant source of the total loss. It has been demonstrated that the selection of a proper dielectric material was the most critical factor in reducing the loss. For further reduction of the loss, the distributed tuning capacitor method and the slotting of the inter-turn spaces have been proposed. For the evaluation of the proposed methods, four coils have been fabricated and their equivalent series resistances and quality factors were measured. Measured quality factors were greater than 300, which means that these devices will be helpful in achieving high coil-to-coil efficiency.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.21 no.2
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• pp.99-109
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• 2010

Recently, SIW(Substrate Integrated Waveguide) is intensively studied because of its high Q and easy integration with other devices. However, lacks of analytic characterization of SIW makes it difficult an accurate design of a SIW filter along the conventional filter design method. In this paper, two kinds of a three-stage 10 GHz SIW bandpass filter of fractional bandwidth 10% are designed using 3D EM simulator HFSS based on the recently presented EM filter design method. Two types of a modified CPW to SIW transition is proposed and employed as a SIW to microstrip transition necessary for measurement. The transitions provide an easy measurement with commercial test fixture by TRL calibration. The two proposed transitions are included in the SIW filters. The fabricated filters shows the center frequency of 10 GHz, fractional bandwidth 10%, a return loss of about 12 dB, and insertion loss of about 0.8 dB.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.3 no.2 s.5
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• pp.85-93
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• 2004

In this paper, microstrip stepped-impedance hairpin resonator (SIR) lowpass filter f.PF) by surface rnicromachining on GaAs substrate is sugsested. This filter has the advantages of compact side, easy fabrication, and sharp cutoff frequency response. The new SIR LPF shows the 3 dB passband of dc to 33 GHz, the insertion loss of 0.82 dB, and the return loss of better than 17 dB up to 25.57 GHz. This filter is useful for many microwave system applications.

• Transactions on Electrical and Electronic Materials
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• v.18 no.2
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• pp.62-65
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• 2017

In this paper, three DC Block designs are presented which efficiently meet the need of modern-day compactsize wireless communication systems. As one of the important parts of a complete system design, the proposed microstrip-based DC block with coupled transmission lines efficiently attenuates unwanted frequencies that cause damage to the system. The compact-sized DC block structures are created by incorporating an extended coupled-line section with a radial stub, an enveloped coupled-line section, and using alternate up-down meandering techniques. The structures are analyzed for the L-Band using a high-resistive silicon substrate. At a resonating frequency of 1.575 GHz, the designed DC Block structures have a return loss better than -10 dB, an insertion loss of around -1 dB, and also possess wide pass-band characteristics.

• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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• 2002.02a
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• pp.159-162
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• 2002

The eleventh-order coupled line lowpass filter(LPF) was designed to suppress harmonics and spurious signals. The microstrip type LPF was fabricated using a high-$T_{c}$ superconductor(HTS) $YBa_{2}$$Cu_{3}$$O_{7-x}$(YBCO) thin film with the $CeO_{2}$ buffer layer which was deposited on the sapphire ($Al_{2}O_{3}$) substrate of 30 x 30 $mm^{2}$. The coupled-line type LPF was designed for 1.2 GHz of cutoff frequency with 0.01 dB of ripple level at passband. The fabricated HTS LPF shows excellent attenuation characteristics in stopband of 1.2~9.5GHz (7-attenuation poles in the stopband), and shows low insertion loss (0.2 dB) and return loss (17.1 dB) in the pass- band. These measured results match well with those obtained by the EM simulation. This clearly demonstrates that the HTS LPF can suppress harmonics and spurious signals effectively.

• Journal of electromagnetic engineering and science
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• v.3 no.1
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• pp.12-16
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• 2003

In this paper, low noise amplifiers with coplanar waveguide structure are presented for Wireless LAN data communication application. For comparison of microwave performance, LNAs of cascode type and balanced type using cascode cell with the same substrate and same bias conditions are designed and implemented. A cascode type of LNA shows the gain of 12.45 ㏈, input return loss of 11.63 ㏈, and noise figure of 1.52㏈. A balanced type of LNA using cascode cell shows the gain of 6.58 ㏈, input return loss of 16.6 ㏈, and noise figure of 1.18 ㏈.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2003.05a
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• pp.97-99
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• 2003

Novel asymmetric 45$^{\circ}$ Schiffman phase shifter having l-coupling for 2.3GHz applications is presented along with measurement results. The proposed phase shifter with a Teflon substrate is fabricated in a smaller area and cost-effective way as compared to the conventional Schiffman phase shifter. In addition, the characteristics of the fabricated phase shifter is extracted and compared. The proposed phase shifter seems useful particularly for the future 2.3GHz wireless applications.

• Transactions on Electrical and Electronic Materials
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• v.15 no.2
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• pp.55-59
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• 2014

An implantable CPW fed monopole antenna embedded into human tissue is proposed for ISM band biomedical applications. The proposed antenna is made compatible for implantation by embedding it in an alumina ceramic substrate (${\Box}_r=9.8$ and thickness=0.65 mm). The proposed antenna covers the ISM band of 2.45 GHz. The radiation parameters, such as return loss, E-Plane, H-Plane, are measured and analyzed, using the method of moments. The proposed antenna has substantial merits over other implanted antennas, like low profile, miniaturization, lower return loss, and better impedance matching and high gain.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.59 no.6
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• pp.1083-1086
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• 2010

The $Sr_{0.7}Bi_{2.3}Nb_2O_9$ thin films were deposited on Si substrate using RF magnetron sputtering method. And the SBN thin films were annealed at 650~800$[^{\circ}C$]. The surface rougness showed about 0.42[nm] in annealed thin film at $650[^{\circ}C$]. The dielectric constant(150) of SBN thin film was obtained by annealing temperature above $700[^{\circ}C$]. The voltage dependence of dielectric loss showed a value within 0.02 in voltage ranges of -10~＋10[V]. The dielectric constant characteristics showed a stable value with the increase of frequency. Also, the SBN thin films annealed at $750[^{\circ}C$] showed a fatigue-free characteristics up to $1.0\times10^8$ cycles.