• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.26 no.1
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• pp.24-29
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• 2015

In this paper, we propose a method of isolation improvement for broadband antennas using a high-permeability substrate. The substrate is applied for a planar monopole antenna based on near-field analysis to maintain radiation characteristics at its operating frequency while improving isolation by minimizing mutual coupling with nearby antennas at other frequency bands. To verify isolation improvement, we compare performance variations of $S_{21}$ according to the existence of the substrate using the proposed antenna and a reference antenna whose operating frequency is 2 GHz. As a result, the radiation characteristics are maintained, and $S_{21}$ performance is improved by more than 5~10 dB in the frequency band of greater than 2 GHz, which demonstrates the isolation can be improved by using the high-permeability substrate.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1995.05a
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• pp.35-38
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• 1995

Indium Tin Oxide(ITO) thin film is transparent to visible ray and conductive in electricity. It is seen that the samples made by the sputtering process have high transmission rate to visible ray and high adhesion , but the planar type magnetron sputtering process with is very well known in industrial region have a defect of partial erosion on the surface of target and a high loss of target and also since the substrate is positioned in plasma, the damage on thin film surface is caused by the reaction with plasma. In cylindrical magnetron sputtering system. it is known that the loss of target is little , the damage of thin film is very little and the adhesion of thin film with substrate is strong. In this study, we have made ITO thin film in the cylindrical DC magnetron system with the variable of substrate temperature , magnetic field, vacuum condution and the applied voltage. The general temperature for formation on ITO is asked at 350 $^{\circ}C$~400$^{\circ}C$ but we have made ITO is low temperature(80-150$^{\circ}C$) By studing electrical and optical properties of ITO thin fims made by varing several condition, we have searched the optimal condition for formation in the best ITO in low temperature.

• The Korean Journal of Ceramics
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• v.5 no.4
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• pp.404-408
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• 1999

Gallium doped zinc oxide(GZO) films were deposited on soda-lime glass substrates without substrate heating $(T_s<50^{\circ}C$) by dc planar magnetron sputtering using GZO ceramic oxide targe with different inert gas (Ar, or Ne). For the GZO films deposited under different total gas pressure $(P_{tot})$, structural and electrical properties were investigated by XRD and Hall effect measurements. Crystallinity of GZO films deposited using Ar was degraded with increase in $(P_{tot})$, suggesting that it was heavily affected by kinetic energy of sputtered Zn particles$(PA_{zn})$ arriving at substrate surface. Whereas, crystallinity of GZO films deposited at lower Ptot than 3.0 Pa using Ne gas was degraded with decrease in $(P_{tot})$. This degradation was considered to be result of film damage caused by the bombardment of high-energy neutrals ($Ne^{\circ}$). On the basis of a hard sphere collision processes, the average final energy of particles (sputtered Zn, $Ar^{\circ}$and $Ne^{\circ}$)arriving at substrate surface were estimated.

• Journal of the Korean institute of surface engineering
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• v.28 no.6
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• pp.386-392
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• 1995

The RF planar magnetron sputtering technique was used to fabricate uniform ZnO/$SiO_2$/Si thin films at high growth rate. A detailed crystallographic character of these thin films has been carried oct using XRD, XRC, and SEM. These thin films have the configuration of c-axis orientation perpendicular to $SiO_2$/ Si substrate. The dependence of the thickness of ZnO/$SiO_2$/Si films on applied RF power parameters was also investigated. The crystallinity of films was improved as the substrate temperature was high, RF input power increased, and Ar/$O_2$ ratio decreased. Also, most of ZnO films fabricated on $SiO_2$/Si were suitable for SAW filter since a standard deviation of XRC (002) peak was less than $6^{\circ}$. The presence of the $SiO_2$ layer has a beneficial effect on the crystalline quality of the grown ZnO films.

• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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• 2003.02a
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• pp.287-290
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• 2003

For microwave device applications, c-axis oriented high temperature superconducting YBa$_2$Cu$_3$O$_{7-{\delta}}$ (HTS-YBCO) epitaxial thin films on the r-cut sapphire substrate(Al$_2$O$_3$) were prepared. In order to reduce the lattice mismatch with a substrate and to enhance the crystallity of HTS thin films, CeO$_2$ buffer layer on the r-cut sapphire substrate was grown by the RF-magnetron sputtering. The YBCO films on the CeO$_2$ buffer layer were deposited using the pulsed-laser deposition (PLD) method. These HTS YBCO /CeO$_2$/Al$_2$O$_3$ multilayer thin films(30 $\times$ 30 mm$^2$) routinely exhibited a critical temperature(T$_{c}$) of 89 K from the R-T measurement. Using HTS YBCO/CeO$_2$ /Al$_2$O$_3$ multilayer thin film. We fabricated and characterized the microwave passive devices (planar type filters) with cryopack-age such as the coupled -line type low-pass filter (LPF) and the open-loop meander type bandpass filter (BPF).filter (BPF).).

• Journal of the Korean institute of surface engineering
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• v.32 no.3
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• pp.467-471
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• 1999

BN films were grown on silicon (l00) substrate by magnetically enhanced activated reactive evaporation (ME-ARE) with pulsed DC power instead of r.f. for substrate biasing. The deposited films were analyzed using Fourier transform infrared spectroscopy (FTIR) and transmission electron microscopy (TEM). FTIR results show that the intensity of absorption band of $sp^2$ bond of BN decreased and that of $sp^3$ bond of c-BN increased with increasing pulsed DC bias voltage applied to substrate. The initially grown layer at the interface was observed by TEM and considered to be of$ sp^2$-bonded BN. The cross-sectional and planar TEM micrographs show that the upper layer on the initial layer was the single phase c-BN. It is concluded that cubic boron nitride films could be synthesized by ME-ARE process with pulsed DC biasing.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.17 no.9
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• pp.1996-2002
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• 2013

In this paper, a design method for a compact broadband planar monopole antenna fed by a coplanar waveguide (CPW) is studied. The proposed broadband monopole is optimized for terrestrial digital television (DTV) reception. In order to achieve broadband characteristics, the monopole and ground conductor are gradually tapered. By loading slit pairs on both monopole and ground plane, the proposed antenna is miniaturized. The monopole is fed by a CPW with 75-ohm characteristic impedance on an FR4 substrate and its size is $100mm{\times}200mm$. The optimized monopole antenna for DTV band (470-806 MHz) is fabricated on an FR4 substrate and tested experimentally to verify the results of this study.

• Korean Journal of Optics and Photonics
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• v.9 no.3
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• pp.156-161
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• 1998

We developed aerosol flame deposition method and made stress-free Pyrex-based optical waveguide on silicon substrate using this method. Zr is doped to control the refractive index of Pyrex waveguide layers. The refractive index of the film changes from 1.460 to 1.475 as the content of Zr changes from 0 to 3 wt%. Er is doped to see the possibility of applying this Pyrex waveguide as PLC-type (Planar Lightwave Circuit) optical amplifier. The refractive index of the film changes from 1.460 to 1.465 as the content of Zr changes from 0 to 1 wt%. Light launching using a prism coupler to the fabricated waveguide showed good quality for application to PLC. The polarization dependence of refractive-index of the Pyrex film is measured to be less than $2{\times}10^{-4}$.

• ETRI Journal
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• v.25 no.2
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• pp.73-80
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• 2003

This paper describes an effective method for forming silicon oxide on silica-on-silicon platforms, which results in excellent characteristics for hybrid integration. Among the many processes involved in fabricating silica-on-silicon platforms with planar lightwave circuits (PLCs), the process for forming silicon oxide on an etched silicon substrate is very important for obtaining transparent silica film because it determines the compatibility at the interface between the silicon and the silica film. To investigate the effects of the formation process of the silicon oxide on the characteristics of the silica PLC platform, we compared two silicon oxide formation processes: thermal oxidation and plasma-enhanced chemical vapor deposition (PECVD). Thermal oxidation in fabricating silica platforms generates defects and a cristobalite crystal phase, which results in deterioration of the optical waveguide characteristics. On the other hand, a silica platform with the silicon oxide layer deposited by PECVD has a transparent planar optical waveguide because the crystal growth of the silica has been suppressed. We confirm that the PECVD method is an effective process for silicon oxide formation for a silica platform with excellent characteristics.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.8 no.3
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• pp.243-253
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• 1997

In land mobile communications, incident waves to mobile antenna com mostly from directions having low elevation angles about $60^{\circ}$ down from the vertical plane. In order to receive this waves effectively, planar type antenna was fabricated and its characteristics were analyzed. This type of antenna is achieved using superstrate effect criteria which are derived for a nonzero radiation field extending down to the substrate layer surface plan. A small planar type microstrip antenna which can receive incident waves having low elevation angle was fabricated. Experimental results show that the band width of the fabricated antenna is 70 MHz at 1.2 GHz and have nonzero field down to the layer surface.