• Journal of electromagnetic engineering and science
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• v.8 no.1
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• pp.28-33
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• 2008

We have proposed a novel DVB-H(Digital Video Broadcast for Handheld) antenna for folder-type mobile handheld terminal by using a coupling element, a stub, and an L-type matching circuit. The L-type matching circuit consisting of two chip inductors is used for achieving an improved impedance matching over the DVB-H frequency band ($470{\sim}702\;MHz$). Simulated results showed the stub worked to more knot the lower and upper frequency ends of the input impedance curve. The antenna exhibits a flat gain characteristic from 2 to 2.8 dBi over the DVB-H frequency band. The radiation patterns are a stable Figure-of-eight radiation pattern in the frequency range.

• Transactions on Electrical and Electronic Materials
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• v.17 no.4
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• pp.217-221
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• 2016

In this work, open and short stubs that were fabricated on the silicon substrate and for which the periodically arrayed grounded-strip structure (PAGS) was employed were studied along with their basic RF characteristics for an applicability regarding the RF-matching components. The PAGS-employing open and short stubs showed losses that are much lower than that of the conventional stub on the silicon substrate. Concretely, the Q values of the open and short stubs are 9 and 10.2, respectively, while the Q value of the conventional open stub is 2.5. With the use of the PAGS-employing open and short stubs, a highly miniaturized harmonic-rejection filter was also fabricated on the silicon substrate. The filter exhibited a comparatively sound harmonic-suppression characteristic at n × 13 GHz, and its size is 0.1 mm², which is only 7% of the size of the conventional filter on the silicon substrate.

• Journal of the Korean Institute of Telematics and Electronics
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• v.24 no.3
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• pp.413-419
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• 1987

In this paper, self-oscillating mixer is designed by small signal S-parameter and series feedback circuit. The input-output matching circuit is accomplished from double stub and additional matching stub. The self-oscillating mixer is oscillating itself and amplifies without any external local oscillator and an intermediate frequency amplifier, so it has advantages in its economical and system simplification. The experimental results show the maximum conversion gain 1.5d B and the noise figure 6.5d B at RF center frequency 4GHz and IF 1.1GHz` output oscillating power 4d Bm, efficiency 13.4%, stability -10MHz/V and -0.5MHz/\ulcornerC at oscillating frequency 5.1GHz.The rejection band loss characteristics in band pass filter and low pass filter are -40d B and -30d B, respectively.

• Journal of the Korean Institute of Telematics and Electronics
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• v.23 no.3
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• pp.317-321
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• 1986

In this paper the design of a new microstrip wide-band microwave discdriminator is presented which is composed of a binary power divider, an open stub and a shorted stub. The microstrip line frequency discriminator is designed at the center frequency of 3.2GHz. Measured discriminating bandwidth is about 20% and return loss is 15dB or more over that frequency range. Experimetal results are in good agreement with the theory.

• Structural Engineering and Mechanics
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• v.88 no.3
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• pp.287-299
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• 2023

This article describes experimental and numerical analyses of eccentrically loaded over the axially loaded circular concrete filled double-skinned steel tubular (CFDST) short columns. Tests on circular CFDST short columns under eccentric and concentric loading were conducted to assess their responses to the frequent intensity of 5-30 mm at the interval of each 5 mm eccentric loading conditions with constant cross-sectional proportions and width-to-thickness ratios of the outside and internal tubes. The non-linear finite-element analysis of circular CFDST short columns of eccentrically loaded over the axially loaded was performed using the ABAQUS to predict the structural behavior and compare the concentric loading capacity over the various eccentric loading conditions. The comparison outcomes show that the axial compressive strength of the circular CDFST short columns was 2.38-32.86%, lesser than the concentrically loaded short column with the inner circular section. Also, the influence of computer simulation employed is more efficient in forecasting the experimentally examined performance of circular CFDST stub columns.

• Journal of Korean Society of Steel Construction
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• v.20 no.5
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• pp.645-653
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• 2008

Welded built-up square tubes are manufactured by flare welding at the center of the column width for cold-formed L-shaped four-piece plates and improved composite effect of concrete and steel by vertical inner anchor. Also, the axial resistance of concrete is increased by the thinness of the steel column, and the composite effect of concrete and steel prevents the steel column from local buckling. In this study, we introduced a manufacturing method of built-up square column steel square concrete-filled tubular column with vertical inner anchor and superior structural performance of the square stub column verified by the structural test for 15 specimens with parameters of shape of tube (built-up square tube, general steel tube), width over thickness of the steel tube (B/t=50, 58, 67) and the strength of concrete (f'c=10MPa, 50MPa).

• Journal of the Korean Institute of Telematics and Electronics D
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• v.35D no.9
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• pp.13-19
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• 1998

It was shown that the bandwidth of T-shaped microstripline fed slot antenna is wider than many of the conventional feeding structures. In this paper, we proposed a new method of enhancing the bandwidth of T-shaped microstripline fed slot antenna with a shunt open stub, and analyzed this antenna by using the FDTD method. We have computed waves and electric field distribution in the time domain, and VSWR, input impedance and radiation pattern in the frequency domaim by Fourier transforming the time domain results. It was found that the bandwidth of this antenna depend on the position(L$_1$) and length(L$_2$) of a shunt open stub. When these parameters are L$_1$=30 mm and L$_2$=33mm, we obtained the maximum bandwidth at the center frequency of 2.3 GHz. From the computed results, the optimum antenna is designed and fabricated. The fractional bandwidth of this antenna was 53.9 %. The measured results were in relatively good accordance with computed values.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.18 no.7
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• pp.698-703
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• 2007

In this paper, a novel impedance tuner using a directional coupler is proposed. The design topology is analyzed by signal flow graph(SFG) and shows advantages compared with conventional single and double stub methods from the view points of easy implementation and wide tuning range, respectively. This impedance tuner consists of ten switches and its $2^{10}$ tuning points are distributed uniformly on the whole Smith chart. The measured maximum magnitude of the reflection coefficient is 0.9. And the fabricated impedance tuner has a wide bandwidth from 1.8 to 2.2 GHz. Using this impedance tuner, we did a load-pull measurement of a power transistor.

• Journal of Korean Society of Steel Construction
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• v.24 no.4
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• pp.435-442
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• 2012

Recently, high performance(strength) steels have been utilized to structural materials in buildings and bridges with the demand for high-rise and long-span of main structures. This paper is a series of basic study for the design specification of structural members using high performance steel, material properties of high performance rolled steel building structures. HSA800 was compared with the requirements of Korean Standards(KS) for HSA800. Welded square tube stub columns with variables of width-to-thickness ratios are planned in order to investigate the local buckling behaviors and check the current design limit of width-to-thickness ratio and uniaxial compressive tests are carried out. In addition, the local buckling behaviors of stub columns obtained finite element analysis were compared with those of test results.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.18 no.11
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• pp.1271-1278
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• 2007

A novel frequency multiplier using composite right/left-handed transmission line is proposed. The left-handed transmission line in the proposed frequency multiplier suppresses the fundamental component($f_0$), while the composite right/left-handed ${\lambda}/4$ open stub diminishes unwanted harmonics. Due to the combination of the left-handed transmission line and composite right/left-handed ${\lambda}/4$ open stub, the only desirable multiplied frequency component such as 3 $f_0$ and 4 $f_0$ are obtained at the output port excellently. For the example of the proposed design, frequency multipliers are designed at 1 GHz of $f_0$ and measured. The measured output power of 3 $f_0$ and 4 $f_0$ is -5.67 dBm and -6.43 dBm, respectively, when the fundamental input power was 0 dBm.