• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.13 no.5
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• pp.468-474
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• 2002

In this paper a novel two-arm microstrip spiral antenna with a circular slot on the ground plane is presented. The proposed antenna structure is constructed in a planar form without a balun circuit and the radiation characteristics of conventional and eccentric spiral antennas are obtained simultaneously. The main beam direction is normal to the plane of the spiral for characteristic frequency band and the direction of the main beam moves linearly into $\theta$ and $\phi$ direction as the frequency increases.

• Tunnel and Underground Space
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• v.20 no.2
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• pp.105-111
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• 2010

This study is to consider applicability of spiral bolt strain gauge as an instrument measuring behavior of soft ground foundation and rock slope. When the instrument was installed on the ground, it can be useful to identify the state of ground behavior because it has the characteristics of flexibility, as well as to apply the ground reinforcement because it has higher pull-out resistance to the ground. From the measurement of behavior to soft ground foundation, the strain shows a stable state in the beginning, then was observed significant change in the upper and the middle of spiral bolt strain gauge after 400 days. This is analyzed that ground loosening, which is due to occurred frequent earthquake of magnitude 1~2 with increased rainfall, lead to the instability of the ground. From the measurement of behavior to rock slope, the strain shows a stable state with very little change in a period of 0~50 days and the biggest strain at 4.2 m (P6) in a period of 50~100 days, then other places except P6 was maintained at a stable state in a period of 100~160 days. The reason is analyzed because that blasting for excavated limestone surrounding was affected to the largest at P6. However, based on the size of strain change by behavior of the soft ground foundation and rock slope, it is considered that the present condition are not effected on stability of retaining structure and rock slope. In conclusion, the proposed spiral bolt strain gauge can be useful to measure behavior of soft ground foundation and rock slope, and also to be measured behavior as well as reinforcement of the target ground.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.19 no.12
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• pp.1322-1332
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• 2008

In this paper, we proposed a divided two-arms spiral slot antenna fed by coplanar waveguide using the magnetic flow at slots. This antenna has characteristics of which one is to short-circuit at the end of the slot and another is to turn spirals separately. To reduce the offset of magnetic flow, two spiral slots are fed by 1800 phase difference. Because we proposed a printed two-arms spiral slot antenna without a balun circuit, antenna size become smaller substantially. And frequency characteristics are studied using the various design parameters. The bandwidth of the realized antenna is $2.7{\sim}12\;GHz$ below the return loss of -10 dB.

• Journal of Bio-Environment Control
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• v.24 no.3
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• pp.202-209
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• 2015

This study compared and analyzed the measurements of pullout load according to the depth of reclamation in the foundation, compaction ratio of soil, spiral diameter, and soil textures in an experiment with a model and reached the following conclusions: The comparison results of extreme pullout load between farm and reclaimed soil show that farmland soil recorded a score that was 1.2~3 times higher than that of reclaimed soil. The investigator measured pullout load in farmland and reclaimed soil and observed a tendency of rising extreme pullout load according to the increasing depth of reclamation and compaction ratio with a similar load-displacement curve between the two types of soil. Extreme pullout load made a greater increase by the rising size of diameter than the increasing depth of reclamation, also making a considerably bigger increase according to the rising compaction ratio than the other conditions. Therefore, the spirals bar is expected to be available in soft soil foundation, as well as farmland as increasing buried deep of foundations, compaction rate, diameter of the spiral, ect.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.13 no.9
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• pp.851-857
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• 2002

A two-arm microstrip spiral antenna with a circular aperture on the ground plane that generates a circularly polarized conical beam is presented in this paper. We obtained circularly polarized conical beam by using two spirals that are excited in-phase from the microstrip feed lines. The main beam directions of the conical beam from the broadside are approximately 40$^{\circ}$ in the range from 5 GHz to 6.5 GHz, and 58$^{\circ}$ from 9 GHz to 11 GHz. Since the proposed antenna has omni-directional conical beam pattern, it is suitable for use in mobile communication systems.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.40 no.11
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• pp.77-84
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• 2003

This paper presents a multi-functional microstrip spital antenna that operates in dual frequency bands. Several types of beam shape can be selected by controlling the phase difference of two spiral arms with the phase shifters located on each feed line. It has a normal beam at the lower frequency band, and four different patterns at the higher frequency band: normal beam, conical beam and two types of tilted beam. The antenna exhibits more than 10% of bandwidth at each band. The antenna is fabricated with conductor backed electromagnetic absorber in order to attain unidirectional radiation pattern and confirmed the multi-functionality by measurements.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.38 no.5
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• pp.16-22
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• 2001

A novel microstrip circular slot antenna fed by a spiral line is presented in this paper. This antenna is a planar equivalent structure of an eccentric spiral antenna generates a circularly-polarized wave. We have investigated the input impedance and radiation characteristics of this antenna by using an EM (electromagnetic) simulator, and obtained a design method [or optimum structure. The main characteristic of the antenna is that the main beam direction is off-normal to the antenna plane and moves linearly into ${\theta }$ and ${\phi }$ direction as the frequency increases. This feature allows one to predict the main beam direction easily for a given operating frequency. This antenna has axial ratio lower than 3 dB in the direction of main beam over one octave bandwidth.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.24 no.1
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• pp.36-46
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• 2013

This paper proposes the design of broadband spiral antenna for a potable non-linear junction detector (NLJD) system. To realize the broadband antenna design, it was considered optimization of the number of spiral turns by iteration calculation. Ground plane with the Archimedean spiral slit to keep the same current distribution between radiating plane and ground is considered for circular polarization design. In order to realize high directivity and high gain of the proposed antenna, the cavity wall and the metal cap which is located on back of ground plane were also considered in design. Measurement results of return loss were agreed well with VSWR 2:1 at interested frequency band among 2.4 to 2.44 GHz, 4.84 to 4.92 GHz and 7.28 to 7.36 GHz. Measured axial ratio was observed 3 dB below and showed reasonable agreement with simulation results. Characteristics of the RHCP(Right Hand Circular Polarization) with the measured gain of 6.8 dBi above at interested frequency band were also observed.

• 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.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.12 no.2
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• pp.142-149
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• 2019

The coils to transmit the electric energy are necessary to charge an electric vehicle wirelessly. There are several types of coils, from basic circular coils to DD-type coils for enhancing the coupling effect between two coils. However, DD-type coils with a good coupling effect between coils have a disadvantage in use because of the structure complexity of the power conversion device of transmitting and receiving side. In this paper, we propose a method to calculate the inductance value and to design the size of the spiral inductor which is convenient to fabricate when the power is transmitted wirelessly by using two coils in free space. Since the bifurcation phenomenon occurs when the XLm value is similar to the load resistance value in the resonator the XLm value was selected to be equal to the minimum load resistance value to minimize this phenomenon, and the inductance value required for the resonator was calculated. In order to realize the calculated inductance value by the spiral inductor, the relationship between the inductance value and the size, the number of turns, the total coil length of a spiral inductor was investigated. In addition, the change of coupling coefficient k according to the horizontal separation of two coils was examined and an appropriate inductor was selected.