• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.25 no.11
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• pp.1104-1112
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• 2014

We present a design of the deployable lightweight antenna to be used in the satellite satisfying the required performance of the onboard sensor. The analysis is performed on the SAR antenna requirements, deploying techniques including material selection, and the characterization of deployable antenna with central disk. The performance of the solid deployable antennas and the mesh antennas are simulated, and the CFRP(Carbon Fiber Reinforced Plastics) samples are manufactured and tested. It is confirmed that the deployable antennas with central disk can meet the required performance by using deploying panels or mesh.

• Journal of Korea Multimedia Society
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• v.11 no.12
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• pp.1697-1705
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• 2008

Several studies made for wireless mesh networks aim to optimize the capacity for wireless networks. Aside from protocol improvements, researches were also done on the physical layer particularly on modulation techniques and antenna efficiency schemes. This paper is concerned with the capacity improvements derived from using spatial diversity with smart adaptive array antennas. The use of spatial diversity, which has been widely proposed for use in cellular networks in order to lessen frequency re-use, can be used in mesh networks both to minimize co-channel interference (CCI) and enable multiple transmissions. This paper aims to study the capacity region and bounds in using smart antennas for single-channel multi-radio systems in relation to the number of spatial diversity or sectors as defined by the beam angle $\beta$.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.35 no.2A
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• pp.134-141
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• 2010

In this paper, we propose a scheduling algorithm to improve the performance of IEEE 802.16 based wireless mesh networks using directional antenna. The performance is presented in terms of throughput of system and delay between each node by varying number of users. The result show that proposed scheduling algorithm improving the performance by reducing the delay of mesh network system. Our work may be useful as a guideline to control the fairness between SSs for multi-hop systems such as multi-hop relay and mesh networks.

• Journal of Aerospace System Engineering
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• v.12 no.2
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• pp.46-58
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• 2018

A two-axis gimbal-type X-band antenna is widely used to transmit bulk image data from high-resolution observation satellites. However, undesirable microvibrations induced by driving the antenna should be attenuated, because they are a main cause of image-quality degradation of the observation satellite. In this study, a pseudoelastic memory alloy (SMA) gear was proposed to attenuate the microvibrations by driving the antenna in an azimuth angle. In addition, the proposed gear can overcome the limitations of the conventional titanium blade gear, which is not still enough and is vulnerable to plastic deformations under excessive torque. To investigate the basic characteristics of the proposed SMA mesh washer gear, a static load test was performed on the thickness of the SMA mesh washer and the rotation of the gear. Moreover, The microvibration measurement test demonstrated that the SMA mesh washer gear proposed in this study is effective for microvibration attenuation.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.47 no.7
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• pp.51-58
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• 2010

Wireless Mesh Network has drawn much attention due to wide area service coverage with low system cost. However, there is a bottleneck problem in wireless mesh network since the traffic is aggregated into a gateway. Placement of multi-radio can easy the bottleneck problem, but without careful design it results in unnecessary system cost increasement. In this paper, we propose a system cost minimization through differential antenna placement where optimum antenna placement is determined by the required wireless link capacity. With CPLEX program, optimum number of antennae is determined as a function of local user traffic and gateway capacity. From numerical analysis, it is confirmed that our proposed model can solve bottleneck problem, and at the same time save the system cost.

• Journal of IKEEE
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• v.23 no.3
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• pp.1112-1115
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• 2019

This paper proposes a novel low-profile omni-directional microstrip antenna to mount on the deployable wing of the observation munition. The proposed antenna is designed on seven hexagonal resonators in a quasi-circular array to achieve a monopolar radiation pattern with a thin substrate. By employing the mesh ground structures, the resonant frequencies and impedance bandwidths of the proposed antenna is investigated. To verify the feasibility of the mesh ground structure, the thin ground wire width is investigated theoretically for improving the 3-dB fractional bandwidth, realized antenna gain and quality-factor. The proposed antenna demonstrates a good monopolar radiation in good agreement with the simulation results. The implemented prototype shows the measured bandwidth of 326 MHz with respect to 5.65% centered at 5.77 GHz and realized gain of 5.49 dBi at 5.84 GHz.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.29 no.7
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• pp.477-483
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• 2018

A transparent antenna designed on the front glass of an automobile operating in the FM broadcast band(88~108 MHz) is proposed. A transparent antenna designed on the front glass of the automobile to avoid space limitation is typically positioned as a roof-mounted shark-fin antenna. An antenna designed on the front glass can reasonably solve the problems of low reception sensitivity and radiated interference from antennas for other service bands. The front glass has a unique closed-line structure, and this structure causes the surface current to flow to the front glass's surroundings; thus, the first resonance is caused before the broadcast band. Through the use of this closed-line structure, the surface current distribution is controlled, and an antenna for which the first resonance is operating in the frequency-modulated(FM) band can be designed. Moreover, the use of a micro-metal-mesh film that is a transparent electrode, suitable for designing a radio frequency device, enables the antenna to minimize visual perception through its transparency. The measured reflection coefficient($S_{11}$) of the antenna is less than -6 dB, and the average peak gain is -0.9 dB in the FM band. Experiments show that the transparent antenna on the front glass offers both the space and design freedom required to develop future automotive antennas.

• Journal of Korea Multimedia Society
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• v.10 no.4
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• pp.516-526
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• 2007

Wireless mesh network is not only WLAN technology but it says core technology for implementation of ubiquitous network and we have to application on a various field through connection with the sensor network. However, there are limited to 100mW in the maximum power because WLAN is used into transmission frequency band to ISM band. The mesh network based on WLAN is essential study for a long distance transmission in the limited maximum power that it is doing to cost-efficient network of backbone. Therefore, in this paper, we have presented an conquerable method to limitation of reaching distance of wireless mesh network and made several experiments to presentation the proposed method. The results show that it is possible to rise a long distance transmission and power efficiency into application of various antenna and function definition and implementation of device driver.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.41 no.10
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• pp.820-826
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• 2013

In this paper, a compact and wideband CLAS(Conformal Load bearing Antenna Structure) was studied using smart skin technique. In order to satisfy the electrical performance of the CLAS antenna, the proposed CLAS antenna is composed of conductive mesh, face-sheet, radiator, honeycomb, housing. Especially, radiator is composed of composite magneto-dielectric material and radiating element etched on the PCB (Printed Circuit Board). The radiating element is inserted into the composite magneto-dielectric material and has sloted Folded LP(Log Periodic) structure. By fabricated composite magneto-dielectric, the resonance frequency is decreased and the impedance matching characteristics is improved. We verified that the antenna has wideband characteristics and compact size using the antenna test results.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2014.10a
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• pp.900-903
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• 2014

Fly-wheel, Gimbal antenna, CMG, Spaceborne cyrocooler generate micro-vibration during their on-orbit operation as well as implementing their own function. To comply with the mission requirement of high resolution observation satellite, additional technical efforts have been required to isolate the micro-vibration derived from such payloads by applying the vibration isolator. In this study, we proposed a passive isolator using SMA mesh washer, which guarantees the structural safety of both micro-vibration disturbance source and itself under harsh launch vibration loads without an additional holding mechanism and the micro-vibration isolation performance on orbit environment. To verify the micro-vibration isolation performance of the proposed vibration isolator, we performed the micro-vibration isolation measurement test using the dedicated micro-vibration measurement device proposed in this study.