• International Journal of Naval Architecture and Ocean Engineering
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• v.4 no.4
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• pp.423-436
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• 2012

Unstiffened plates are integral part of all kinds of structures such as ship and offshore oil platforms. Openings are unavoidable and absolutely reduce the ultimate strength of structures. In this study, the finite element analysis package, ABAQUS, is used to analyze the behavior of unstiffened plate with rectangular opening. The rectangular opening form is divided into two cases. In case1, opening depth is constant, but opening width is varied. Meanwhile, in case2 opening width is fixed and opening depth is varied. Besides, for the two different form opening, the effect of plate slenderness parameter (${\beta}$), opening area ratio (AR) and opening position ratio (PR) on the ultimate strength of plate with opening under axial compression are presented. It has been found that the ultimate strength of plate ofcase1is much more sensitive to the plate slenderness parameter (${\beta}$) and opening area ratio (AR) than that of case2. However, for case1, opening position (PR) almost has no effect on the ultimate strength, whereas, regardingcase2, the influence of opening position (PR) depends on the plate slenderness parameter (${\beta}$). Based on nonlinear regression analysis, three design formulae are not only developed but also approved reasonably for the practical engineering design.

• ETRI Journal
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• v.34 no.5
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• pp.767-770
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• 2012

This letter presents a novel compact circularly polarized patch antenna for Global Positioning System/Global Navigation Satellite System (GPS/GLONASS) applications. The proposed antenna is composed of a simple square radiating patch fed by a capacitive dual-feeder to increase the impedance bandwidth and a lumped element hybrid coupler to achieve the broadband characteristic of the axial ratio (AR). The realized antenna dimensions are $28mm{\times}28mm{\times}4mm$, which is the most compact size among the dual-band GPS/GLONASS antennas reported to date. The measured results demonstrate that the proposed antenna has a gain of 2.5 dBi to 4.2 dBi and an AR of 0.41 dB to 1.51 dB over the GPS/GLONASS L1 band (1.575 GHz to 1.61 GHz).

• Proceedings of the Korea Electromagnetic Engineering Society Conference
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• 2003.11a
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• pp.459-463
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• 2003

A circularly polarized microstrip patch antenna (MPA) using electromagnetic (EM) coupled fed method is analyzed in view of the two types of coupling mechanisms viz. cavity and parasitic type, proposed earlier. The patch-ground plane distance is varied in order to achieve the fore-mentioned types of couplings. For each case of patch-ground plane distance, the offset position of feedline is optimized for perfect matching and the boresight axial ratio (AR) is observed. It is seen that CP operation is possible only for cavity-type coupling (smaller patch-ground plane distances). The simulated results for the boresight AR for the two types of coupling mechanisms are presented.

• Journal of electromagnetic engineering and science
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• v.12 no.2
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• pp.155-160
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• 2012

A wideband circularly polarized pinwheel-shaped planar monopole antenna fed by a wideband feeding network is presented in this paper. The proposed antenna is formed by four wideband planar monopole antenna elements with aquadruple feeding network in order to improve the performance of circular polarization. Additionally, the antenna, which is introduced here, has a high gain in the z axis direction because of its folded antenna structure. The attractive characteristics of the proposed antenna are the wide impedance bandwidth of 87.3 % (1 GHz to 2.55 GHz), the 3 dB axial ratio (AR) bandwidth of 92.3 % (1.05 GHz to 2.85 GHz), and the maximum gain within the 3 dB AR bandwidth is about 8.24 dBic.

• Journal of electromagnetic engineering and science
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• v.14 no.4
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• pp.360-366
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• 2014

A single-feed composite cavity-backed four-arm curl antenna is presented for use in global positioning systems (GPS). Its primary radiating element is fed by a vacant-quarter printed ring, which helps the antenna directly match to a $50-{\Omega}$ coaxial line and produce a good circular polarization (CP). The cavity-backed reflector is employed to improve the CP radiation characteristics in terms of 3-dB axial ratio (AR) beamwidth and minimum AR value. The optimized design with an overall size of $90{\times}90{\times}25mm^3$ ($0.4725{\lambda}_o{\times}0.4725{\lambda}_o{\times}0.13{\lambda}_o$ at 1,575 MHz) results in a ${\mid}S_{11}{\mid}<-10dB$ bandwidth of 8.66% (1,514-1,651 MHz) and a 3-dB AR bandwidth of 2.23% (1,555-1,590 MHz). The antenna radiates a widebeam right-hand circular polarization and operates with a measured radiation efficiency greater than 90% within its impedance matching bandwidth.

• Journal of electromagnetic engineering and science
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• v.17 no.1
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• pp.1-8
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• 2017

This paper introduces a technique to obtain the broadband characteristics of circularly polarized antennas using an L-shaped probe. A waveguide antenna is suitable for obtaining high gain and handling convenience in some applications; however, the asymmetrical structure of the L-shaped probe results in cross-polarization and frequency dependence on the field distribution of higher-order modes (HOM). In addition to the basic characteristics of a waveguide antenna with an L-shaped probe, the author discusses some techniques to reduce the HOM and cross-polarization. As a result, the 3-dB axial ratio (AR) is obtained with the fundamental mode even when the frequency is expanded to the region for HOM of TM. This reduction is mainly due to the cutoff structure to the TM mode around the short wall of the waveguide. Furthermore, some aperture modification techniques can reduce the cross-polarization in a wide range of angles in the radiation pattern. Such techniques and their mechanisms are discussed in this paper. The obtained performance shows that the proposed antennas have a wide range of angles of 3-dB AR in the radiation pattern, broadband characteristics in impedance and AR, and low variation in group velocity.

• Journal of the Korea Society of Computer and Information
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• v.15 no.7
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• pp.67-74
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• 2010

TIn this paper, it is designed the 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 it has under 3dB AR(axial ratio). Peak gain of antenna is 7.71dBi, 7.55dBi with linear polarization and 7.31dBic, 7.81dBic with circular polarization at x-y plane. Also Axial ratio of antenna is 2.01~2.83dB and 2.02~2.60dB respectively. It is satisfied 3dB axial ratio.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2006.05a
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• pp.595-598
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• 2006

In this letter, a compact rectangular spiral antenna is proposed. Instead of a center excitation of conventional spiral antennas, the proposed antenna is adopted a modified feed network, feeding at the end of the spiral. The matching circuit of $'{\sqsupset}'$ shape is added at the feeding point. With this matching circuit, we can easily match the input impedance well, without the limit of the space. The parameter which determines the circular wave characteristic is explained, and the design guideline of the proposed antenna is presented. We design a proposed antenna operating at 9.5 GHz. Its size is only $0.6\lambda_g\times0.6\lambda_g$. The simulated bandwidth of the input impedance $(S11\leq-10)$ is 8.12% and that of $(AR\leq-3)$ is 4.62%, which is excellent characteristics as compared to its simple structure.

• Journal of electromagnetic engineering and science
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• v.14 no.3
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• pp.299-305
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• 2014

A wideband circularly polarized (CP) antenna with a single feed is proposed for use in global navigation satellite systems. Its primary radiation elements are composed of two orthogonal bowtie dipoles, which are equipped with double-printed vacant-quarter rings to allow direct matching of the antenna to a single $50-{\Omega}$ coaxial line and to produce CP radiation. The crossed bowtie dipole is appropriately incorporated with a planar metallic reflector to produce the desired unidirectional radiation pattern as well as to achieve a wideband characteristic in terms of impedance matching and axial ratio (AR) bandwidths. The designed antenna was fabricated and measured. The prototype antenna with an overall 1.2-GHz frequency size of $0.48{\lambda}_o{\times}0.48{\lambda}_o{\times}0.25{\lambda}_o$ produced a measured ${\mid}S_{11}{\mid}$<-10 dB bandwidth of 1.05-1.79 GHz and a measured 3-dB AR bandwidth of 1.12-1.64 GHz. It also showed right-hand CP radiation with a small gain variation (${\pm}0.3dB$) and high radiation efficiency (>93%) over the operational bandwidth.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.17 no.5
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• pp.128-134
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• 2018

In this paper, two ports feeding a microstrip patch antenna using a quadrature hybrid circuit was proposed to enhance the bandwidth for the global positioning system(GPS). The square patch was designed, and the probe feeding was applied. The quadrature hybrid chip circuit for two-port feeding was designed, and output ports that have a 90-degree phase difference feed to the patch antenna. The designed patch and quadrature hybrid circuit were implemented on an FR4 board, and were combined. The measurement of the bandwidth within a voltage standing wave ratio(VSWR) of 2:1 and axial ratio(AR) in 3dB were wide band as 29% BW (1,230~1,700 MHz) and 15.87% BW (1,400~1,650 MHz), respectively. Antenna gain were measured 2.75dBi at the center frequency.