• 디지털융복합연구
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• 제10권4호
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• pp.265-270
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• 2012

최근 기간망의 전송속도는 괄목할 만한 성장을 이루고 있으나 가입자 전송망의 전송속도는 이전 수준에 비교해서 진정이 없는 상태이다. 그래서 가입자 접속 구간은 다수의 LAN과 백본망 사이에 병목지점으로 지적되고 있다. 현재 가입자 구간은 VOD, 양방향게임, 양방향 영상회의와 같은 새로운 대용량 멀티미디어 서비스를 수용하기에 충분한 대역폭을 제공하지 못하고 있다. 그런 가운데 저가의 이더넷 장비와 광선로 인프라를 융합한 EPON(Ethernet Passive Optical Network)이 차세대 가입자 접속망에 가장 적합하다. 하지만 이러한 우수성을 가진 EPON도 안정적인 대용량 멀티미디어 서비스를 제공하기에는 부족함을 가지고 있다. EPON에서 ONU가 수신할 수 있는 대역폭은 1GBPS이지만 송신하기 위한 대역폭은 모든 ONU가 공유해야 하므로 부족하다. 따라서 양방향 초고속 가입자 접속망을 위해 FTTx를 지원하는 EPON의 부족한 상향 전송 대역폭을 충족시키는 상향 대역폭 할당 방법이 필요하다. 본 논문에서는 EPON의 상향 트래픽에 대한 QoS를 보장하기 위한 우선순위 큐를 고려한 가중치 기반의 차등대역폭 할당 방식을 제안한다.

• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 2000년도 춘계종합학술대회
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• pp.489-492
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• 2000

This paper describes a new transient voltage suppressor(TVS) with a low insertion loss and a very wide frequency bandwidth to protect antenna circuit from transient voltages. Conventional protection devices have some problems such as low frequency bandwidth and high insertion loss. In order to improve these limitations, a coaxal type TVS, which consists of a gas tube is developed. The performance of the proposed transient voltage suppressor is tested by using a combination surge generator specified in IEC 61000-4-5 standard and by using a network analyzer of 40 MHz ∼ 5GHz bandwidth. From the experimental results, it is confirmed that the proposed TVS has an enough protection performance in low insertion loss and in wide frequency bandwidth

• JSTS:Journal of Semiconductor Technology and Science
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• 제13권4호
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• pp.263-271
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• 2013

A low dropout regulator (LDO) with fast transient responses is presented. The proposed LDO eliminates the trade-off between slew rate and unity gain bandwidth, which are the key parameters for fast transient responses. In the proposed buffer, by changing the slew current path, the slew rate and unity gain bandwidth can be controlled independently. Implemented in $0.18-{\mu}m$ high voltage CMOS, the proposed LDO shows up to 200 mA load current with 0.2 V dropout voltage for $1{\mu}F$ output capacitance. The measured maximum transient output voltage variation, minimum quiescent current at no load condition, and maximum unity gain frequency are 24 mV, $7.5{\mu}A$, and higher than 1 MHz, respectively.

• Journal of electromagnetic engineering and science
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• 제17권4호
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• pp.202-207
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• 2017

This paper presents the performance of a planar, low-profile, and wide-gain-bandwidth leaky-wave slit antenna in different thickness values of high-permittivity gallium arsenide substrates at terahertz frequencies. The proposed antenna designs consisted of a periodic array of $5{\times}5$ metallic square patches and a planar feeding structure. The patch array was printed on the top side of the substrate, and the feeding structure, which is an open-ended leaky-wave slot line, was etched on the bottom side of the substrate. The antenna performed as a Fabry-Perot cavity antenna at high thickness levels ($H=160{\mu}m$ and $H=80{\mu}m$), thus exhibiting high gain but a narrow gain bandwidth. At low thickness levels ($H=40{\mu}m$ and $H=20{\mu}m$), it performed as a metasurface antenna and showed wide-gain-bandwidth characteristics with a low gain value. Aside from the advantage of achieving useful characteristics for different antennas by just changing the substrate thickness, the proposed antenna design exhibited a low profile, easy integration into circuit boards, and excellent low-cost mass production suitability.

• Journal of Information Processing Systems
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• 제19권6호
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• pp.817-829
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• 2023

Variable wireless channel is a big challenge for real-time video applications, and the rate adaptation of realtime video streaming becomes a hot topic. Intra-video coding is important for high-quality video communication and industrial video applications. In this paper, we proposed a novel adaptive scheme for real-time video transmission with intra-only coding over a wireless network. The key idea of this scheme is to estimate the instantaneous remaining capacity of the network to adjust the quality of the next several video frames, which not only can keep low queuing delay and ensure video quality, but also can respond to bandwidth changes quickly. We compare our scheme with three different schemes in the video transmission system. The experimental results show that our scheme has higher bandwidth utilization and faster bandwidth change response, while maintaining low queuing delay.

• 한국정보통신학회논문지
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• 제9권3호
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• pp.582-586
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• 2005

본 논문은 locking 상태에 따라서 루프대역폭이 변화하는 Phase Locked Loop (PLL)의 구조를 제안하였다. 제안한 PLL은 기본적인 PLL 블록과 NOR Gate, Inverter, Capacitor, 그리고 Schmitt trigger로 이루어진 Locking Status Indicator(LSI) 블록으로 구성되었다. LSI는 Loop Fille.(LF)에 공급되는 전류와 저항 값을 locking 상태에 따라 변화시켜서 unlock이 되면 넓은 루프대역폭 가지는 PLL로, lock이 되면 좁은 루프대역폭을 가지는 PLL로 동작하도록 한다. 이러한 구조의 PLL은 짧은 locking 시간과 저 잡음의 특성을 동시에 만족시킬 수 있다. 제안된 PLL은 Hynix CMOS $0.35{\mu}m$ 공정으로 Hspice 시뮬레이션 하였으며 40us의 짧은 locking 시간과 -76.1dBc 크기의 spur를 가진다.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2010년도 추계학술대회 논문집
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• pp.565-566
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• 2010

• Journal of Mechanical Science and Technology
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• 제17권4호
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• pp.511-520
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• 2003

In room acoustics, reverberation time is an important acoustic parameter. However it is often difficult to measure short reverberation times at low frequencies with a traditional band pass filter bank if the product of filter bandwidth (B) and reverberation time (T) is small. It it well known that the minimum permissible product of bandwidth and reverberation time of the traditional band pass filter is at least 16. This strict requirement makes it difficult to measure short reverberation times of an acoustic room at low frequencies exactly. In order to reduce this strict requirement, in the previous paper, the wavelet filter bank was developed and the minimum permissible product of bandwidth and reverberation time was replaced with 4. In the present paper it is demonstrated how the short reverberation times of an practical room at low frequencies are successfully measured by using the wavelet filter bank and the results are compared with the traditional method using a band past filer bank.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2002년도 춘계학술대회논문집
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• pp.1077-1080
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• 2002

In building acoustics, reverberation time is an important acoustic parameter. However, it is often difficult to measure short reverberation times at low frequencies using the traditional band pass filter bank if the product of bandwidth (B) and reverberation time (T) is small. It is well known that the minimum permissible product of bandwidth and reverberation time of the traditional band pass filter is at least 16 ［F. Jacobsen, J. Sound Vib. 115, 163-170 (1987)]. This strict requirement makes it difficult to measure short reverberation times of an acoustic room at low frequencies exactly. In order to reduce this strict requirement, recently, the wavelet filter bank is developed and the minimum permissible product of bandwidth and reverberation time is replaced with 4 [S. K. Lee, J, Sound Vib. 252, 141-153 (2002)]. In the present paper, it is demonstrated how the short reverberation times at low frequencies are successfully measured by using the wavelet filter bank. In order to present this job, two synthetic signals and one measured signal are used for impulse responses of an acoustic room.

• Journal of Power Electronics
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• 제15권6호
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• pp.1673-1681
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• 2015

A low dropout (LDO) regulator with a wide-bandwidth is proposed in this paper. The regulator features a Human Body Model (HBM) 8kV-class high robustness ElectroStatic Discharge (ESD) protection circuit, and two error amplifiers (one with low gain and wide bandwidth, and the other with high gain and narrow bandwidth). The dual error amplifiers are located within the feedback loop of the LDO regulator, and they selectively amplify the signal according to its ripples. The proposed LDO regulator is more efficient in its regulation process because of its selective amplification according to frequency and bandwidth. Furthermore, the proposed regulator has the same gain as a conventional LDO at 62 dB with a 130 kHz-wide bandwidth, which is approximately 3.5 times that of a conventional LDO. The proposed device presents a fast response with improved load and line regulation characteristics. In addition, to prevent an increase in the area of the circuit, a body-driven fabrication technique was used for the error amplifier and the pass transistor. The proposed LDO regulator has an input voltage range of 2.5 V to 4.5 V, and it provides a load current of 100 mA in an output voltage range of 1.2 V to 4.1 V. In addition, to prevent damage in the Integrated Circuit (IC) as a result of static electricity, the reliability of IC was improved by embedding a self-produced 8 kV-class (Chip level) ESD protection circuit of a P-substrate-Triggered Silicon Controlled Rectifier (PTSCR) type with high robustness characteristics.