• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.19 no.2
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• pp.237-243
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• 2008

This paper presents the backplane effects for two-wire transmission line with different line length crossing the rectangular aperture in an infinite ground backplane. The FDTD method is used to determine the characteristics of the backplane insertion loss and return loss of the transmission line in accordance with the transmission line spacing and additional wire lengths. The results show that the insertion gain is obtained for the narrow spacing of the transmission line and the insertion loss is appeared for the transmission line with the additional wire The measurements of return loss are performed to verify the theoretical analysis.

• The Journal of Asian Finance, Economics and Business
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• v.7 no.9
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• pp.105-115
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• 2020

The study empirically examines the effects of loan portfolio diversification on bank risk and return in the nascent banking market of Vietnam. Loan portfolio diversification is captured through the Hirschman-Herfindahl index and the Shannon Entropy with sectoral exposures. We access each bank's financial reports to collect the required data, especially the breakdown of sectoral loan portfolios, thus constituting a unique dataset. To compute bank return, we use the traditional accounting indicators, including return-on-assets, return-on-equity, and net-interest margin. For bank risk, we utilize the loan-loss provisions and non-performing loans relative to gross customer loans. Using a sample of 30 commercial banks over the period from 2008 to 2019 and the system generalized method of moments estimator for the dynamic panel, we indicate the downsides of portfolio diversification. Concretely, we observe that all diversification measures exhibit significantly negative signs in all regressions across different bank return proxies. At the same time, the estimates display the significant and positive impact of diversification on the non-performing loan ratio. Hence, sectoral loan portfolio diversification significantly hampers bank performance in both aspects of lower return and higher credit risk. The results are robust across a rich set of bank performance and portfolio diversification measures.

• International Journal of Fluid Machinery and Systems
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• v.1 no.1
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• pp.86-91
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• 2008

The effects of the diffuser vane on the performances of the multistage centrifugal pump were investigated experimentally, taking account of the interactions among the diffuser vane, the return vane, and the next stage impeller. It is very important to match well the diffuser vane with the return vane, for improving the hydraulic efficiency of the pump. The efficiency may be more improved by making the cross-sectional area of the channel from the diffuser vane outlet to the return vane inlet larger, as much as possible.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.06a
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• pp.50-51
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• 2009

This paper presents integrated passive device (IPD) based on Wilkinson power divider. The simulated 2-way power divider has the insertion loss of 3.123 dB, output isolation of -24.576 dB, input return loss of 26.415 dB, and output return loss of 33.478 dB. The power divider is based on IPD process design simulation at 2.5 GHz for WiMAX (Worldwide Interoperability for Microwave Access) applications. The chip size of power divider is $1\;\times\;1.2\;mm^2$, which is under fabrication.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.18 no.8
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• pp.759-765
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• 2005

In this paper, developed isolator for gap filler is analyzed and designed using the simulation tool. Using the designed parameters, isolator is fabricated and tested in gap filler band. Temperature characteristics of isolator depend on magnet, YIG ferrite, and conductor etc. These require temperature stability and possible method of compensation for the temperature dependent effects. The temperature stabilization tries to use Ni-alloy. Developed isolator that compare with room temperature and high temperature characteristics has change fewer than 20 MHz. Implemented isolator shows more than 20 dB isolation characteristic at center frequency(2,650 MHz) and has 0.2 dB insertion loss in overall 100 MHz operating bandwidth. Return losses of input and output port are measured below -20 dB.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.5 no.7
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• pp.1321-1325
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• 2001

In this article, piezoelectric films and their application for film bulk acoustic resonator (FBAR) devices are presented. The FBAR is composed of piezoelectric film sandwiched between top and bottom electrodes and an acoustic reflector of SiO2/W stacked multilayers. Various FBAR devices were fabricated and evaluated through simulation and measurement. The insertion loss, return loss and Q-factor were observed to be reasonably high and good. The FBAR technology seems very promising particularly for RF band filter application.

• Journal of the Korean Ceramic Society
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• v.43 no.9 s.292
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• pp.527-531
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• 2006

In order to study the influence of post-annealing treatment on the frequency characteristics of the Li doped ZnO(Li:ZnO) FBAR(Film Bulk Acoustic Resonator) device, we investigated the material and electrical properties of Li:ZnO films in the annealing temperature range from 300 to $500^{\circ}C$. In our samples, as annealing temperature was increased, Li:ZnO films showed the improvement of high c-axis orientation and resistance value with relieved stress and low surface roughness. In addition to, the return loss in the frequency property of fabricated FBAR was improved by annealing treatment from 24.9 to 29.8dB. From experimental results, the optimum post-annealing temperature for FBAR is $500^{\circ}C$ and it can obtain excellent Li:ZnO FBAR performance with stronger c-axis orientation, smoother surface, relieved stress, and lower loss factor.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2001.10a
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• pp.621-625
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• 2001

In this article, piezoelectric films and their application for film bulk acoustic resonator (FBAR) devices are presented. The FBAR is composed of piezoelectric film sandwiched between top and bottom electrodes and an acoustic reflector of SiO$_2$/W slatted multilayers. Various FBAR devices were fabricated and evaluated through simulation and measurement. The insertion loss, return loss and Q-factor were observed to be reasonably high and good. The FBAR technology seems very promising particularly for RF band filter application.

• Journal of electromagnetic engineering and science
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• v.12 no.2
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• pp.171-175
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• 2012

In this work, a new microstrip-to-substrate integrated waveguide (SIW) transition using the parallel half-mode substrate integrated waveguide (HMSIW) is proposed. The proposed transition consists of three sections : a microstrip, parallel HMSIWs, and an SIW. By inserting the parallel HMSIWs section between the microstrip section and the SIW section, the proposed transition can improve the return loss characteristics of the near cut-off frequency because the HMSIWs section has a lower cut-off frequency than the SIW section (8.6 GHz). The lower cut-off frequency is achieved through gradual electromagnetic field mode changes for a low reflection. The measured return loss is less than 20 dB in the of 9.1~16.28 GHz freqeuncy range for the back-to-back transition. The measured insertion loss is within 1.6 dB for the back-to-back transition. The proposed transition is expected to play an important role in wideband SIW circuits fed by a microstrip.

• ETRI Journal
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• v.35 no.4
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• pp.638-643
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• 2013

This paper presents a 5-bit digital step attenuator (DSA) using a commercial 0.18-${\mu}m$ silicon-on-insulator (SOI) process for the wideband phased array antenna. Both low insertion loss and low root mean square (RMS) phase error and amplitude error are achieved employing two attenuation topologies of the switched path attenuator and the switched T-type attenuator. The attenuation coverage of 31 dB with a least significant bit of 1 dB is achieved at DC to 20 GHz. The RMS phase error and amplitude error are less than $2.5^{\circ}$ and less than 0.5 dB, respectively. The measured insertion loss of the reference state is less than 5.5 dB at 10 GHz. The input return loss and output return loss are each less than 12 dB at DC to 20 GHz. The current consumption is nearly zero with a voltage supply of 1.8 V. The chip size is $0.93mm{\times}0.68mm$, including pads. To the best of the authors' knowledge, this is the first demonstration of a low phase error DC-to-20-GHz SOI DSA.