• ETRI Journal
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• v.37 no.1
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• pp.26-31
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• 2015

Axial-ratio (AR) bandwidth enhancement is achieved for a circularly polarized (CP) cylindrical dielectric resonator antenna (DRA) using a wideband hybrid coupler (WHC) combined with dual probe feed. The presented WHC, comprised of a Wilkinson power divider and a wideband $90^{\circ}$ shifter, delivers good characteristics in terms of 3 dB power splitting and consistent $90^{\circ}$ (${\pm}5^{\circ}$) phase shifting over a wide bandwidth. In turn, the proposed CP DRA, for the employment of the WHC, in place of conventional designs, provides a significant enhancement on AR bandwidth and impedance matching. The antenna prototype with the WHC exhibits a 3 dB AR bandwidth of 48.66%, an impedance bandwidth of 52.5% for voltage standing wave ratio (VSWR) ${\leq}2$, and a bandwidth of 44.66% for a gain of no less than 3 dBi. Experiments demonstrate that the proposed WHC is suitable for broadband CP DRA design.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.6 no.3
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• pp.440-444
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• 2002

A microstrip patch antenna with circular polarization based on the Sierpinski fractal geometry is proposed. The Sierpinski fractal is composed of 3 equilaterial triangular patch and is easy to produce a circular polarization by sequentially rotation techniques. The characteristics of a 1x3 antenna array from Sierpinski geometry are investigated, i.e. port isolation and AR(axial Ratio).

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2002.05a
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• pp.234-237
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• 2002

A microstrip patch antenna with circular polarization based on the Sierpinski fractal is composed of 3 equilaterial triangular Polarization by sequentially rotation techniques. The characteristics of a $1\times3$ antenna array from Sierpinski geometry an investigated, i.e. port isolation and AR(axial Ratio).

• ETRI Journal
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• v.41 no.3
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• pp.289-297
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• 2019

In this paper, a wideband, circularly polarized patch antenna is proposed that leverages the unidirectional resonant modes of a circular patch mounted on top of a grounded dielectric-ferrite substrate. The proposed antenna is fed via the proximity coupling method and several parasitically coupled patches are placed on a dielectric superstrate to enhance the impedance bandwidth of the antenna. The resonant modes of the structure rotate only in the clockwise or counter clockwise directions. In the frequency range where the effective permeability of the ferrite layer is negative, the resonance frequencies of these modes differ significantly, which produces a large axial ratio (AR) bandwidth. For the proposed antenna, the numerical results show the 10 dB impedance bandwidth to be around 44% and the 3 dB axial ratio bandwidth to be higher than 64%.

• Structural Engineering and Mechanics
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• v.36 no.1
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• pp.1-18
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• 2010

A total of 28 wall panels were cast and tested under uniformly distributed axial load in one-way in-plane action to study the effect of slenderness ratio (SR) and aspect ratio (AR) on the ultimate load. Two concrete formulations, normal concrete (NC) and self compacting concrete (SCC), were used for the casting of wall panels. Out of 28 wall panels, 12 were made of NC and the remaining 16 panels were of SCC. All the 12 NC panels and 12 out of 16 SCC panels were used to study the influence of SR and the remaining 4 SCC panels were tested to study the effect of AR on the ultimate load. A brief review of studies available in literature on the strength and behaviour of reinforced concrete (RC) wall panels is presented. Load-deformation response was recorded and analyzed. The ultimate load of SCC wall panels decreases non-linearly with the increase in SR and decreases linearly with increasing values of AR. Based on this study a method is proposed to predict the ultimate load of reinforced SCC wall panels. The modified method includes the effect of SR, AR and concrete strength.

• Proceedings of the Korea Concrete Institute Conference
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• 1998.10b
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• pp.615-620
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• 1998

The objective of this experimental study is to investigate the hysteretic behavior of reinforced concrete piers subjected to quasi-static cyclic loads, which have been used in large numbers for railway and urban transportation facilities. Important test parameters are hoop ratio, axial load, loading type, and the behaviors f members have been evaluated through limit states of crack occurrence, yielding and ultimate state of member, ductility and load-deflection loop can be secured by considering the influence of hoop reinforcement ratio and axial load, and that plastic hinge length and ductility ar determined by the combination of the quantities of hoop reinforcement and axial load.

• Journal of Advanced Navigation Technology
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• v.14 no.2
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• pp.170-175
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• 2010

This article proposed polarization selective antenna for UHF RFID system. The proposed antenna is consist of microstrip patch antenna with dual feeding and two SPDT switches and a SP4T switch and 3dB hybrid coupler. Through control of voltage of switches, the proposed reader antenna can select horizontally linear polarization, vertically linear polarization, left-hand circular polarization (LHCP) and right hand circular polarization (RHCP). The proposed reader antenna satisfied 2:1 VSWR at 902MHz ~ 928MHz. and 3dB under AR(axial ratio). And it can select appropriative polarization with user environment and tag polarization. So it minimize PLF and increased reading distance.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.14 no.6
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• pp.281-289
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• 2004

The temperature hump is found to be most efficient in suppressing parasitic nucleation. With the temperature humps, there are found to be observed in undersaturations along the transport path for convective-diffusive processes ranging from $D_{AB}$ = 0.0584 $\textrm{cm}^2$/s to 0.584 $\textrm{cm}^2$/s, axial positions from 0 to 7.5 cm. With decreasing Ar = 5 to 3.5, the temperature difference is increased because of the imposed nonlinear temperature profile but the rate is decreased. For 2 $\leq$ Ar $\leq$ 3.5, the rate is increased with the aspect ratio as well as the temperature difference. Such an occurrence of a critical aspect ratio is likely to be due to the effect of sidewall and much small temperature difference. The rate is decreased exponentially with the aspect ratio for 2 $\leq$ Ar $\leq$ 10. Also, the rate is exponentially decreased with partial pressure of component B, P for 1 $\leq$ P $\leq$ 100 Torr.$ B/ $\leq$ 100 Torr.

• ETRI Journal
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• v.40 no.5
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• pp.561-569
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• 2018

Modern communication systems employ wideband antennas with circular polarization (CP) radiation. In this work, asymmetric modified bow-tie (ABT) and symmetric modified bow-tie (SBT) slotted circularly polarized single-point probe-fed circular patch antennas with dimensions of $40mm{\times}40mm$ for wideband applications are proposed. A 10 dB RL bandwidth of 350 MHz with CP, 3 dB axial ratio (AR) bandwidth of 100 MHz, peak gain of 4.9 dBic, and 10 dB RL bandwidth of 530 MHz with CP, 3 dB AR bandwidth of 140 MHz, peak gain of 5 dBic are obtained for ABT and SBT slotted circular patch antennas, respectively. The proposed SBT slotted patch is scaled up and down to $50mm{\times}50mm$ and $30mm{\times}30mm$, respectively. The proposed scaled-up version offers 10 dB RL and 3 dB AR bandwidths of 340 MHz and 80 MHz, with a peak gain of 5 dBic. The scaled-down version offers 10 dB RL and 3 dB AR bandwidths of 710 MHz and 180 MHz, with a peak gain of 5.25 dBic. These prototypes are suitable to work in IEEE 802.11a WLAN, ISM, and IEEE 802.11ac applications. The measured and simulated results are then discussed and compared.

• Proceedings of the KIEE Conference
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• 1999.11d
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• pp.959-961
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• 1999

ZnO thin films are deposited by using an RF magnetron sputtering system. Structural and electrical properties are analyzed as a function of deposition conditions, such as RF power, Ar/($Ar+O_2$) ratio, and substrate temperature. The c-axial growth of ZnO is observed to be preferable to the $SiO_2$/Si substrate, rather than the Si substrate. By adding the oxygen gas during deposition, the electrical resistivity of films is increased, but the c-axial growth is inhibited. A pizoelectric resonator of Al/ZnO/Al is also fabricated to estimate the electric-mechanical coupling coefficient($k^2$) of ZnO film. The value of $k^2$ obtained from our work is about 10.14 %.