• Proceedings of the Optical Society of Korea Conference
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• 2008.07a
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• pp.405-406
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• 2008

In this paper, we will discuss the spectral characteristics of fiber Bragg gratings (FBGs) inscribed in two different types of polarization-maintaining fibers with side holes. One showed high signal-to-noise ratio (SNR), narrow bandwidth and high bending sensitivity, while the other one showed insensitivity to bending due to the small size of the side holes.

• Vacuum Magazine
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• v.4 no.4
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• pp.14-17
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• 2017

Recently, quantum-dots light emitting diodes (QLEDs) are considered as a next-generation display due to the superior luminescence behaviors, photo stability and narrow spectral emission bandwidth. Moreover, the emission color of QLEDs can be easily controlled by changing the dimension of quantum dots (QDs). A flexible display based on QLEDs can be achieved using low-cost solution process, such as a printing technology. Therefore, QLEDs are expected as a next generation display. In this document, recent progresses in QDs technology will be introduced.

• Proceedings of the Optical Society of Korea Conference
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• 2003.07a
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• pp.198-199
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• 2003

광섬유 브래그 격자(Fiber Bragg Grating, FBG)는 좁은 선폭과 적은 삽입손실 등의 뛰어난 스펙트럼 특성을 가지고 있어, 고밀도 파장분할 다중화 방식을 이용한 광통신 시스템과 여러 종류의 광섬유센서에 응용되고 있다. 브래그 격자의 광학적 스펙트럼을 능동적으로 조절하기 위하여, 광섬유에 열이나 스트레인을 인가하거나, 음파와 빛의 결합을 이용한 방법이 제안되었으며, 특히 음향 광학 브래그 격자 변조기(Acousto-Optic Superlattice Modulator)는 종 방향 음파(Longitudinal Acoustic Wave)를 이용하여 파장과 크기의 조절이 가능한 사이드 밴드(Side Band)를 생성해 내었다. (중략)

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.13 no.8
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• pp.769-776
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• 2002

In this paper, we propose uniform slot width bow-tie-shaped meander slot antenna for 5 GHz application. The conventional bow-tie slot antenna has broadband characteristic, however, its size is large. Meanwhile, the meander slot antenna has small size, but it has quite narrow bandwidth. The proposed antenna geometry is a variation of the meander slot antenna incorporating bow-tie shape to realize miniaturized antenna having relatively large bandwidth. Simulated results show that with the same slot width and total slot length, the bandwidth of the proposed antenna is 3 times wider than that of meander slot antenna, and its resonant frequency is 3.01 GHz lower than that of the equal size(H x V) bow-tie slot antenna, and measured results show that the bandwidth of proposed antenna is 218 MHz(5.142 GHz ~ 5.360 GHz) which satisfy the required bandwidth from 5.15 GHz to 5.35 GHz.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.21 no.5
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• pp.33-39
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• 2021

In this study, we tried to find the correlation of the parameters and dual resonance of U-slot microstrip patch antenna with L-shaped Inset-feed structure and design broadband antenna using them. In the first step, we classified cases where dual resonance occurs through changes in antenna parameters that affect antenna performance. In the second step, we correlated each antenna parameter to the location and intensity of the resonance point, and 3 dB bandwidth. Next, antenna simulation confirmed the process of designing to have wide bandwidth using the correlation in the second step previously presented in the U-slot antenna case with narrow bandwidth. Finally, we fabricated a designed antenna and demonstrated the validity of antenna bandwidth broadening through the correlation analysis.

• The Transactions of the Korea Information Processing Society
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• v.5 no.11
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• pp.2763-2775
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• 1998

In mobile computing environments, to efficiently use the narrow bandwidth of wireless networks a mobile host caches the data that are frequently accessed. But, because the cached data can be inconsistent with the data n a server due to the host mobility and the disconnection from a server, the usefullness of cached data may be losted. The traditional methods emphasize on the cache consistency and assume that broadcasting times are synchronized at all mobile supprot stations. In this paper, we propose a strategy to maintain cache consistency, which resolves the problems that be caused by the migration of mobile host. The proposed strategy has asynchronous broadcasting time and reduces the communication overhead caused by the synchronization. Also, by preventing the unnecessary messages transmitting from the mobile support station to a mobile host, this strategy can reduce the communication cost and use the narrow bandwidth of wireless networks efficiently.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.15 no.6
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• pp.554-559
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• 2004

A novel miniaturized 2-pole band pass filter(BPF) is proposed and it has an overlapped hairpin and slot structure on the upper and bottom plane of microstrip lines. Due to the overlapped structure of a hairpin and a slot, the size of the proposed BPF is quite smaller than that of a general BPF having coupled lines. The size of the proposed BPF is reduced to 33 % comparing with the conventional λ/4 coupled BPF. The attenuation is improved by controlling the attenuation poles properly using the proposed structure. The proposed 2-pole BPF is fabricated with a narrow bandwidth(69 ㎒) at center frequency, 1.9 ㎓ which is difficult to make that narrow bandwidth in the conventional coupled lines due to impractical spacing. The design method in this paper can be applied to the design of other microwave circuits to reduce the size and improve the performances.

• Journal of the Korea Institute of Military Science and Technology
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• v.13 no.3
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• pp.397-404
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• 2010

Recently, there is on-going research about tactical data link system based on the legacy radio. Tactical data link based on legacy radio is operated mostly in narrow bandwidth under 25khz. Communicating traffics in nodes participated at network need to be minimized for distributing tactical data in narrow bandwidth. In addition, the data distributing structure is necessary for distributing tactical informations such as a situation awareness and so on to war fighters. However, conventional server-client system wastes a lot of time to obtain information for war fighters as user uses pull system to gather necessary information by seeking it one by one. Especially, the fighter pilot is supposed to dedicate into a situation awareness and fight mission in every seconds but seeking information of a user terminal while aircraft maneuvering affects as obstacle to concentrate engaging hostiles. therefore, push technology, the tactical data distributing system, is necessary for war fighters to receive fixed tactical data automatically without putting attention to it. This paper propose the UMPC tactical data link push framework. the UMPC tactical data link is a tactical data link system based on the legacy radio. Proposed push framework is verified by composing experiment environment and testing.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.12 no.5
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• pp.857-862
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• 2008

This paper evaluate the performance using a simulated 490KHz narrow band filter based on characteristic parameters appropriately extracted from 490KHz band-pass filter after considering each characteristic, which is modeled on equivalent circuit and applied to NAVTEX receiver using crystal oscillator. The evaluation results show that the value of a series capacitor of crystal oscillator has only little capacity by Cs=21.094fF and the bandwidth characteristics of filter go worse as the capacity value of crystal oscillator grow increase. Moreover, the series inductance value of crystal oscillator has a relatively big value by L=5H, therefore the bandwidth characteristic according as inductance's capacity shows more little effect than the capacity.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.13 no.4
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• pp.393-400
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• 2002

In this paper, a novel series feeding cross-aperture coupled microstrip antenna with the effect of hybrid feeding is proposed and demonstrated experimentally to improve narrow axial ratio bandwidth of cross-aperture coupled antenna with single feeding among the various methods for generating circular polarization. The validity of a proposed series feeding cross-aperture coupled microstrip antenna is shown by comparing experimental results between the reported and the proposed microstrip antenna, and 2${\times}$2 array microstrip antenna based on the proposed single microstrip antenna used sequential rotation technique to accomplish broader axial ratio bandwidth. In the proposed single and 2${\times}$2 array microstrip antenna, the measured axial ratio bandwidths are 110 ㎒(4.6%) and 420 ㎒(17.5%), maximum gains are 8.2 ㏈i and 12.5 ㏈i, 3 dB gain bandwidths are above 400 ㎒(16.7%), and impedance bandwidths for the VSWR<1.5 are 240 ㎒(10%) and 500 ㎒(20.8%), respectively.