• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.19 no.12
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• pp.1416-1426
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• 2008

In this paper, we present a small size and multiband directional dipole antenna for mobile communication repeaters. In the omni-directional dipole antenna, a planar reflector under the dipole provides improved directivity in front-direction with wide beamwidth. In order to miniaturize the directive dipole, the size of the reflector is reduced. A vertical stub on the reflector is proposed to enhance the front-directivity of the radiation pattern and mitigate the backward radiation due to the reduced reflector. Furthermore, we use horizontal stubs on edge of vertical stub to obtain additional reduction of the antenna size. To meet the current demand of wireless communication service, the designed antenna shows wideband characteristic by employing electromagnetic coupled two-dipoles with dual-resonance frequencies.

• Journal of Biomedical Engineering Research
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• v.29 no.3
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• pp.187-190
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• 2008

This paper presents two dimensional receiving coils to provide hundreds of milli-watt power via inductive link to in vivo robotic capsules, whose orientation are practically undetermined. The wireless power transmission system consists of a transmitter powered by class E power amplifier, and a receiver with three dimensional antenna, rectifier, and voltage regulator. As the 2D lateral antenna construction is more critical for the receiving antenna, two types of 2D antennas are introduced and evaluated by theoretic and experimental analyses. Experimental results verifies that the cross-type construction show better directional performance for receiving power than the cylindrical one for the 2D antenna. The former could deliver the power homogeneously regardless of its orientation, with less than 20 % of variation from the possible maximum power.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.7 no.2
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• pp.43-49
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• 2008

In this paper, new directional couplers for T/R switch of UHF RFID applications are proposed to overcome TX-to-RX leakage problem. The proposed method can remove TX-to-RX leakage caused by both imperfect isolation characteristic of the conventional directional coupler and the mismatch of antenna impedance. Two directional couplers are implemented using distributed elements and lumped elements respectively for the verification. The varactor tuneable circuits for compensation of the antenna mismatch is also proposed. The measurement result shows excellent TX-to-RX leakage suppression, more than 45dB in 910MHz.

• Proceedings of the KSRS Conference
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• 2000.04a
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• pp.125-130
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• 2000

This paper deals with antenna configurations of a two-antenna synthetic aperture microwave radiometer for the high spatial resolution and precision of brightness temperature measurements. Four different types of antenna configurations are considered. The directional patterns of each type are compared in the paper.

• Progress in Superconductivity
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• v.2 no.1
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• pp.51-55
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• 2000

A $Y_1Ba_2Cu_3O_{7-\delta}$ square spiral microstrip antenna (YBCO antenna) was epitaxially grown on a $LaAlO_3$ substrate by laser ablation. Also fabricated was a gold square spiral microstrip antenna (gold antenna) having the same structure as that of the YBCO antenna in order to compare the properties of both antennas. Both the YBCO antenna and the gold antenna were operated in Ku (12-18 GHz) band, and their properties such as the return loss, SWR, power gain, and radiation patterns were investigated at 77 K. The return loss below -10 dB was obtained in two frequency ranges, i.e., 14.05-14.90 GHz, and 16-18 GHz for the YBCO antenna at 77 K (YBCO superconducting antenna), and in the frequency range of 15.05-17.60 GHz for the gold antenna at 77 K. The SWR bandwidths are 0.85 GHz and 2 GHz for the YBCO superconducting antenna, and 2.55 GHz for the gold antenna at 77 K. The gain improvement of the superconducting YBCO antenna over the gold antenna at 77 K was about 10 dB in the frequency range of 16 GHz to 18 GHz. The radiation patterns show the YBCO superconducting antenna has the omni-directional property of a spiral antenna.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37 no.1B
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• pp.9-14
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• 2012

The neighbor discovery using directional antennas in mmWave band is a prerequisite for communications and this issue is crucial and urgent. In this paper, the synchronized, direct, two-way directional neighbor discovery process is analyzed mathematically for mmWave WPANs. The analysis is based on the values which are derived from the effect of using directional antennas. The neighbor discovery probability for a given amount of time is considered and several performance measures such as the optimal sojourn time are derived in closed forms. Numerical results are obtained using parameters based on the IEEE 802.15.3c. The mathematical analysis provides the theoretical basis for the directional neighbor discovery process.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37C no.9
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• pp.802-810
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• 2012

This paper describes RFID(Radio Frequency Identification) based target acquisition and docking system. RFID is non-contact identification system, which can send relatively large amount of information using RF signal. Robot employing RFID reader can identify neighboring tag attached objects without any other sensing or supporting systems such as vision sensor. However, the current RFID does not provide spatial information of the identified object, the target docking problem remains in order to execute a task in a real environment. For the problem, the direction sensing RFID reader is developed using a dual-directional antenna. The dual-directional antenna is an antenna set, which is composed of perpendicularly positioned two identical directional antennas. By comparing the received signal strength in each antenna, the robot can know the DOA (Direction of Arrival) of transmitted RF signal. In practice, the DOA estimation poses a significant technical challenge, since the RF signal is easily distorted by the surrounded environmental conditions. Therefore, the robot loses its way to the target in an electromagnetically disturbed environment. For the problem, the g-filter based error correction algorithm is developed in this paper. The algorithm reduces the error using the difference of variances between current estimated and the previously filtered directions. The simulation and experiment results clearly demonstrate that the robot equipped with the developed system can successfully dock to a target tag in obstacles-cluttered environment.

• Journal of Industrial Technology
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• v.22 no.B
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• pp.155-161
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• 2002

As the wireless communications are gradually developed, the higher frequency is demanded and the smaller the size of antenna shall be reduced by the wavelength of the operating frequency. However, the smaller the size of antenna becomes, the less the gain is obtained according to the frequency, so that a new attempt such as an array antenna has been examined to improve the characteristics. Also, for the convenience of communication, the omni-directional property is required. In this paper, two antennas system which is aligned in cross direction in tested and analyzed. The main scope is focused to get an appropriated distance between the two small antennas to get better properties. There are various ways of array arrangement, but in this study, it should be placed on the same PCB for easy implementation and the direction of each antenna are aligned to be a cross($90^{\circ}$) position. The study is carried out by comparing the radiation patterns mainly, and the theoretical expectation and the computer simulation are also executed. The final model is the folded IF-antennas system printed on PCB and the ideal dipole-antenna arrangement in also test to verify the possibility of our implementation. And it is finally proved by measuring experiments.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.43 no.4 s.346
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• pp.31-37
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• 2006

Strongly motivated by the need for significant reduction in the optics-to-antenna interface circuitry used in a Photonically controlled array, it has proposed the design development of a novel 'true photonic antenna' consisted of optical fiber and micro-strip antenna. To clarify the design capability of the geometry, modal transmission-line theory including the discontinuity property between circular i,nd planar guiding structures is defined, md the optical power coupling of a slot-coupled microstrip antenna directly fed from an optical fiber using photoconductive effect is evaluated numerically. The numerical results reveal that the maximum power transfer between the two different guiding structures occurs at a new point in which the guiding powers of two rigorous modes are equally partitioned.

• Proceedings of the KSRS Conference
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• 2002.10a
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• pp.235-240
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• 2002

This paper shows the desist concept of an ATS(Antenna Tracking Software) to control the movement of the MSC(Multi-Spectral Camera) antenna. The MSC has a two-axes directional X-band antenna for image transmission to KGS(KOMSAT2 Ground Station). The main objective of the ATS is to drive the APM(Antenna Pointing Mechanism) to the required elevation and the azimuth position according to an appropriate TPF(Tracking Parameter File). The ATS is implemented as one task of the SBC(Single Board Computer) software, which uses VxWorks as a real time OS. The ATS has several operational modes such as STANDBY mode, First EL mode, First AZ mode, Normal Operation mode, and so on. The ATS uses two PI controllers fur the velocity and the position loop respectively, to satisfy the requirements specification. In order to show the feasibility of the described design concept, the various simulations and the experiments are performed under specific test configuration.