• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.3A
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• pp.296-303
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• 2008

Co-existence of various wireless systems may cause frequency interference problem. For this reason, frequency sharing studies play a very important role in order to use limited spectrum resources efficiently. Especially, because a satellite system covers a global area in nature, the frequency sharing between the satellite system and terrestrial systems is essential. For satellite systems using Ka bands, we can increase spectrum efficiency by considering off-axis angles of earth station antenna. In this paper, we demonstrate the analysis result of separation distance between the satellite earth station and a terrestrial repeater, and the presented results can be used to design and implement Ka band wireless systems.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.11 no.8
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• pp.1355-1362
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• 2000

Microstrip antennas are attractive for many applications because of their compact size, low profile, and light weight. Recently, the demand for the miniaturization of the personal communication equipment has been increasing along with the proliferation of personal communication systems. Thus, the development of small antenna has been highly demanded. In this paper, a new technique to reduce the overall dimension of a microstrip antenna with a locally non-homogeneous substrate configuration is proposed. The miniaturized microstrip antenna for a repeater system in a mobile communication cellular band(824~894 MHz) is designed with the proposed technique, and commercialized with low cost, light weight, and small size. Comparison between simulations, based on Agilent Technologies HFSS software, and measurements are provided. The proposed method will be more attractive for a light-weight, small-size, and low-cost microstrip array design. This paper also presents the bandwidth improvement technique for under-coupled microstrip patch antenna with a tuning stub.

• Journal of the Korean Institute of Navigation
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• v.10 no.1
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• pp.81-100
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• 1986

Self-contained portable remote-indicating magnetic compass was designed and tested. Its sensing part consists of main scale disk of rotary encoder with photo-etched 180, oopaque slits and three pairs of light sources and detectors seperated by a transparent index scale, so that any angular deflection of main scale disk against the bowl may be detected optically. The outputs from the sensing part are transformed into digital ship's course indication by electronics unit which consists of operational amplifier, phase discriminator, up-down counter and counting starter circuit. The results from testign the above compass with turntable at variable rate of turn are as following : 1) The main scale disk deflection against the bowl can be detected without any disturbing influence to the freedom of its north-seeking function. 2) The digital indication resolution is found to be $\circ \pm$1 degree. 3) Misrepresenting indication can be avoided by ensuring dimension uniformity and arrangement accuracy of slits on main and index scale disks and by centering pivot in the encoder disk. 4) Indication resolution should be improved by modifying the signal processing and by doubling the number of slits on compass card. 5) Further study should be made on developing non-conductive compass liquid, analogue repeater driving system and more compact processing element.

• Journal of Satellite, Information and Communications
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• v.8 no.2
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• pp.22-28
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• 2013

In this paper, new LBS (location based service) are proposed using conventional DMB (digital multimedia/mobile broadcasting) system. LBS applications are proposed that can be suitable for the subway and ground transportation based on S-DMB (satellite-DMB) and T-DMB (terrestrial-DMB) respectively. In the shaded area such as subway, the broadcasting signal transmitted from the satellite of S-DMB system should be retransmitted by the earth repeater called the gap filler and each gap filler has its own identification value called the gap filler ID which introduces the area in which the gap filler was installed. Therefore, the LBS can be implemented by using the gap filler ID of S-DMB on the subway in which the GPS (global positioning system) can't be received. Unlike the LBS on the subway, the combination of T-DMB and DGPS (differential GPS) will be introduced as a way for ground transportation. Generally, DGPS has been designed to compensate the position value calculated from the GPS signal so that positioning error of about 1 meter can be obtained by using DGPS information. T-DMB system transmitting DGPS signal will be expected to be commercial in Korea and, if using DGPS information transmitted through T-DMB network, LBS with more precise positioning than GPS alone can be implemented in the ground vehicles.

• 한국정보통신설비학회:학술대회논문집
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• 2008.08a
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• pp.3-6
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• 2008

In this paper, we propose the folded PIFA with its made an alteration to a factor of resonance for L-slot PIFA. Proposed antenna maintain diminished size patch and improve each bandwidth of GSM(0.88$\sim$-0.96 GHz) and W-CDMA(1.92$\sim$2,17 GHz) for miniaturized repeater. The non-slot step folded PIFA's structure that design of essence was general L-slot PIFA for dual-band. It has no U-slot, multi band and the another slot. The parameters of proposed antenna were optimized for dual-band and compact size by folded singleness patch. Proposed antenna by using folded singleness patch take satisfaction main point, bandwidth of GSM and W-CDMA, compact patch size($39{\times}21{\times}13mm^3$). The antenna was designed by FDTD simulation tool and it was made from result of simulation. Measured data shown that the proposed non-slot step folded PIFA was strong possibility.

• Journal of Power Electronics
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• v.17 no.6
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• pp.1694-1706
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• 2017

Models and experiments for magnetic resonance coupling wireless power transmission (MRC-WPT) topologies such as the chain topology and branch topology are studied in this paper. Coupling mode theory based energy resonance models are built for the two topologies. Complete energy resonance models including input items, loss coefficients, and coupling coefficients are built for the two topologies. The storage and the oscillation model of the resonant energy are built in the time domain. The effect of the excitation item, loss item, and coupling coefficients on MRC systems are provided in detail. By solving the energy oscillation time domain model, distance enhancing models are established for the chain topology, and energy relocating models are established for the branch topology. Under the assumption that there are no couplings between every other coil or between loads, the maximum transmission capacity conditions are found for the chain topology, and energy distribution models are established for the branch topology. A MRC-WPT experiment was carried out for the verification of the above model. The maximum transmission distance enhancement condition for the chain topology, and the energy allocation model for the branch topology were verified by experiments.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.12 no.1
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• pp.183-188
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• 2008

Satellite DMB(Digital Multimedia Broadcasting) uses the Cap Filler(GF) that provides a service to the wave shade area of the satellite signal that is a non-line of sight area. The GF is the repeater and the Satellite DMB Systems certainly must construct the GF Network toguarantee the movement reception of the terminal. As the coverage of the GF is formed the Cell or Sector, when the multiple GF is established to be contiguous, the problem of the interference will be able to occur. This paper describes the Satellite DMB system and the GF, and it investigate the design fundamentals plan of the GF Network that it will be able to reduce this problem. As a result, in case of the distance that GF and terminal unit is above 4.6Km, service is not provided because of quality degradation according to mutual interference.

• Korean Journal of Optics and Photonics
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• v.17 no.5
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• pp.396-400
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• 2006

We present a weather-insensitive optical free-space communication method supporting optical packet channels. It operates optical fiber amplifiers in gain-saturation regions. When the propagation loss gets too high, it decreases the average packet rate, or the average packet length, or both, to increase the optical power level launched into the free-space. As a demonstration, we transmit $8{\times}10$ Gigabit Ethernet channels over a terrestrial distance of 2.4 km. One gain-saturated free-space optical repeater is used at the halfway point.

• Journal of the Korea Society of Computer and Information
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• v.27 no.1
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• pp.33-41
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• 2022

This paper describes a planar microstrip patch antenna designed on dielectric substrate. Two types of planar microstrip patch antennas are studied for the 5G wireless applications, one type is conventional microstrip structure, the other type is stacked microstrip structure fed by coaxial probe. Using electromagnetically coupling method, stacked microstrip patch antenna employing a multi-layer substrate structure was designed. The results indicate that the proposed stacked microstrip patch antenna performs well at 5G wireless service bandwith a broadband from 3.42GHz to 3.70GHz. The impedance bandwidth(VSWR≤2) is 360MHz(10.28%) from 3.42GHz to 3.78GHz. In this paper, through the designing of a stacked microstrip patch antenna, we have presented the availability for 5G wireless repeater system.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2008.05a
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• pp.121-124
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• 2008

In this paper, we will design a 800MHz broadband antenna after a problem of the narrow bandwidth is improved. This multiple band antenna unifies the CDMA(Code Division Multiple Access), GSM(Global System for Mobile telecommunication) and TRS(Trunked Radio System) band in the UHF bandwidth, and then it is possible at the shore base station or repeater as the commercial use. It used the duplex resonance effect It had the L-shaped feeding structure which adds the V-slot. And it improved profit using stack structure. It was measured that the frequency bandwidth of the designed antenna which is planed $792{\sim}1040MHz$ with 248MHz(33%). And the antenna gain is 9.4dBi, 3dB beam width $60^{\circ}$ in radiation pattern.