• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2010.06a
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• pp.342-342
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• 2010

This paper mainly focuses and describes four-armed dual-band rectangular type patch antenna using teflon of 0.54 mm thickness substrate for the application in personal wireless communications at about 2 GHz and 2.5 GHz frequency ranges. The dual-band patch antenna is obtained by embedding one centered and two pairs of rectangular patches on single body above the substrate. Details of the proposed antenna design are presented and discussed as a novel design with remarkable value of return loss (S11) of -28.68 dB and it is the most suitable for WiMAX applications as well.

• Journal of electromagnetic engineering and science
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• v.1 no.1
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• pp.43-47
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• 2001

A compact size microstrip antenna element using FR-4 substrate is proposed for use in repeater and base stations. Two stacked patches are aperture-coupled by two split feedlines. Rectangular stubs on the split feedlines are laid under the aperture and have the effect of considerably lowing the magnitude of $S_{11}$ [dB] and broadening impedance bandwidth. The designed structure has been fabricated and measured. Based on 20 dB, the return loss bandwidth is about 16.8% (1.86 GHz~2.20 GHz), which covers the frequency range assigned for IMT-2000 with a large margin. The overall dimension of the proposed antenna structure is 37 mm$\times$41 mm$\times$19mm (very compact). The antenna gain is more than 7.5 dBi over the required frequency range.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• v.9 no.1
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• pp.371-375
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• 2005

In this paper, the resonance characteristics of ZnO-based FBAR devices are compared. Several FBAR device samples were fabricated by using three different annealing methods while one sample remained non-annealed as a reference for comparison. Resonance characteristics could be significantly improved by both Bragg reflector-annealing and/or post-annealing steps. Especially, the use of two-step annealings resulted in most desirable resonance characteristic improvement compared with the Bragg reflector-annealing or post-annealing step alone.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• v.9 no.2
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• pp.320-324
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• 2005

In this paper, the resonance characteristics of SMR-type FBAR devices annealed by three different annealing methods are investigated and compared. The resonance characteristics could be effectively improved by the proposed efficient annealing method which can optimize the annealing conditions. It seems very useful for improving the performance of the SMR-type FBAR devices in a cost-effective way.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.53 no.8
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• pp.443-446
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• 2004

In this paper, a multi-band ceramic chip antenna for WLAN(Wireless LAN) applications is designed. The design target is to obtain 0 dBi of coverage gain with omni directional radiation pattern. The antenna is fabricated using Low Temperature Co-fired Ceramic(LTCC) technology. The size of the chip antenna is $2.2{\times}9.65{\times}1.02$mm. The measured antenna gain is 1 dBi at 2.44 GHz and 0.5 dBi at 5.5 GHz. The omni directional radiation pattern for the two operating bands is obtained. The measured bandwidth(S11=-10 dB) are 90 MHz at 2.44 GHz and 1280 MHz at 5.5 GHz respectively

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.39 no.9
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• pp.11-18
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• 2002

This paper presents a CPW phase shifter and shunt stub with air-bridge on a 10-${\mu}m$-thick oxidized porous silicon(OPS) substrate using surface micromachining. The line dimensions of the CPW phase shifter was designed with S-W-Sg = 100-30-400 ${\mu}m$. And the width and length of the air-bridge with "ㄷ“ shape were 100 ${\mu}m$ and 400-460-400 ${\mu}m$, respectively. In order to achieve low attenuation, stepped air-bridge CPW phase shift was proposed. The insertion loss of the stepped air-bridge CPW phase shift is more improved than that of no stepped air-bridge CPW phase shift. The measured phase characteristic of the fabricated CPW phase shifter is close to 180$^{\circ}$ over a very broad frequency range of 28 GHz. The measured working frequency of short-end series stub is 28.7 GHz and the return loss is - 20 dB. And the measured working frequency of short-end shunt stub is 28.9 GHz and the return loss is - 23 dB at midband. As a result, the pattering of stub in the center conductor of CPW lines can offer size reduction and lead to high density chip layouts.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.40 no.5
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• pp.938-943
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• 2015

The proposed circular patch antenna was designed to include relative bandwidth of above 25% as designed by the FCC in the FCC in the 3.1 ~ 10.6 GHz band. The antenna was induced to have a wide band characteristic through two structures of the usual microstrip line and a microstrip line with a linear change in impedance. The proposed finally antenna was designed using an FR4_epoxy substrate with 4.7% permittivity, 0.02 of loss tangent, and 1.6 mm of thickness, and was simulated with the use of HFSS made by Ansys. Return loss at frequency, VSWR, radiation pattern and the gain of the antenna were analysed. As a result, if satisfied a return loss of -10 dB and $VSWR{\leq}2$ from 2.28 ~ 13.35 GHz, showing about the bandwidth of 11.89 GHz, and the radiation pattern was unidirectional in all bands. The antenna gain gradually increased from 2 ~ 8 GHz and had the highest gain of 7.92 dBi at 8 GHz. and the gain gradually decreased in the 9 ~ 12 GHz band.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.42 no.3
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• pp.333-342
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• 2022

Due to climate change, increased heavy rainfalls result in flood damage every year. To investigate the storm-runoff reduction effects of Low Impact Development (LID), this study performed runoff analyses using the U.S. Environmental Protection Agency (EPA) Storm Water Management Model (SWMM) for past and future representative storm events of the Yongdu Rainwater Pumping Station basin. As a result, the infiltration loss for representative future rainfalls increased by 3.17 %, and the surface runoff and peak runoff rate increased significantly by 32.50 %, and 128.77 %, respectively. To reduce the increased surface runoff and peak runoff rates, this study investigated the applicability of LID approaches, including a permeable pavement, green roof, and rain garden, by adjusting the LID parameters and the ratio of installation area. We identified the ranges of LID parameters that decreased peak runoff rate and surface runoff, and increased infiltration. In addition, when the application ratio of permeable pavement, green roof, and rain garden was 2:1:3, best performance was attained, leading to a reduction of peak runoff of 26.85 %, infiltration loss 12.01 %, surface runoff 15.11 %, and storage 509.47 %. Based on analyzing the effect of storm runoff reductions for various return periods, it was found that as the return period increased, the proportion of peak runoff and surface runoff increased and the proportion of infiltration loss and storage decreased.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.11 no.9
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• pp.1642-1649
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• 2007

The lumped element isolators with temperature compensation magnetic circuits were designed in this paper. Isolators for mobile repeater at each band of K-PCS, GSM1900, W-CDMA, WiBro were fabricated by using optimum parameters of EM simulation, Form the results of this study, first of all, insertion loss at K-PCS band was below 0.2 dB and return loss was over 25dB. The bandwidth in isolation 23dB was found 30 MHz. Secondly, the figures of both losses at GSM1900 were 0.25dB and 23dB, respectively. The measured bandwidth in isolation 30dB was 60MHz. Thirdly, the losses at W-CDMA band were 0.15dB and 25dB. The bandwidth in isolation 24.8dB was found 60Mhz. Finally, the figures of both losses at Wibro band were 0.25dB and 23dB, respectively. The measured bandwidth in isolation 22.1dB was 100Mhz. In addition, the results of measured IMD were shown from 76.4dBc to 80.1dBc.

• Journal of Satellite, Information and Communications
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• v.11 no.4
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• pp.44-47
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• 2016

In these days, interest of systems and services using TVWS(TV White Space) are increased, communication systems and services for TVWS have been actively studied. The unoccupied frequency in TVWS is different according to the geographical location and the time of day. RF systems having a frequency tunable bandpass filter operated in TVWS could be efficiently used. In this paper, a frequency tunable bandpass filter operated in 470 ~ 698MHz is designed and implemented. In consideration of simple control and physical size, the tunable bandpass filter is designed with 2-pole. The implemented tunable bandpass filter has the operating frequency band of 470 ~ 698MHz with control voltages of 1.58 ~ 3.93V, the insertion loss of maximum 4.78dB and the return loss of below 10dB. The implemented frequency tunable bandpass filter can be directly used in the RF receiver for TVWS and the design procedures could be used for developing a high power tunable bandpass filter as the basic research data.