• 한국통신학회:학술대회논문집
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• 한국통신학회 2004년도 추계종합학술대회 논문 초록집
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• pp.413-413
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• 2004

• 전자공학회지
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• 제30권3호
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• pp.295-295
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• 2003

The advantages of using analogue optical networks for delivering radio signals from a central location to many remote antenna sites have been recognized. In a telecommnications context, radio signals may be for fixed radio access, cordless or mobile networks, but the same principles apply. By making use of the high bandwidth, low loss characteristics of optical fiber, all high frequency and signal processing functions can be performed centrally and signals can then be transported over the optical network directly at the carrier frequency. The remote sites then become very simple, requiring only optoelectronic conversion, filtering and linear amplification. This shifting of the complex functionality away from the remote site allow cheap, reliable, small and light-weight radio access points with low power consumption to be deployed. In this paper, we show that an electroabsorption modulation(EAM) may be used as a single component in such a radio access point, as a passive transceiver for small-sized cell(picocells).

• 전자공학회지
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• 제30권3호
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• pp.81-85
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• 2003

The advantages of using analogue optical networks for delivering radio signals from a central location to many remote antenna sites have been recognized. In a telecommnications context, radio signals may be for fixed radio access, cordless or mobile networks, but the same principles apply. By making use of the high bandwidth, low loss characteristics of optical fiber, all high frequency and signal processing functions can be performed centrally and signals can then be transported over the optical network directly at the carrier frequency. The remote sites then become very simple, requiring only optoelectronic conversion, filtering and linear amplification. This shifting of the complex functionality away from the remote site allow cheap, reliable, small and light-weight radio access points with low power consumption to be deployed. In this paper, we show that an electroabsorption modulation(EAM) may be used as a single component in such a radio access point, as a passive transceiver for small-sized cell(picocells).

• 한국전자파학회논문지
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• 제29권1호
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• pp.10-19
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• 2018

본 논문에서는 고주파 Radio-Frequency Interference (RFI) 측정용 프로브로 널리 쓰이는 Printed Spiral Coil(PSC)의 고주파 등가회로 모델이 제안되었다. 제안된 모델은 고주파 정합성을 확보하기 위하여 PSC의 설계변수에 기반한 분포 모델로 설계되었으며, 제안된 분포 등가회로 모델을 바탕으로 T-Pi 등가변환을 이용한 PSC의 고주파 해석적 모델 역시 새로이 제안되었다. 제안된 모델의 실제 고주파 RFI 측정 시 효용성을 확인하기 위하여, 임의의 RFI 노이즈 원으로 설계된 마이크로스트립 라인과 PSC 사이의 전달함수를 제안된 모델과 상호 인덕턴스를 결합하여 추출하였다. 제안된 PSC 모델의 자기 임피던스(self-impedance)와 전달함수는 3-dimensional field solver를 이용한 시뮬레이션 및 실 측정으로 검증되었으며, 6 GHz까지 높은 정합성을 보이는 것이 확인되었다. 제안된 PSC의 자기 임피던스 및 전달함수 모델은 GHz 영역의 고주파 통신대역에서의 RFI 측정용 프로브 설계 및 노이즈 간섭 예측에 활용될 수 있다.

• ETRI Journal
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• 제29권5호
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• pp.569-595
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• 2007

Particularly in wireless communications, link errors severely affect the quality of the services due to the high error probability and the specific error characteristics (burst errors) in the radio access part of the network. In this work, we show that thorough analysis and appropriate modeling of radio-link error behavior are essential to evaluate and optimize higher layer protocols and services. They are also the basis for finding network-aware cross-layer processing algorithms which are capable of exploiting the specific properties of the link error statistics, such as predictability. This document presents the analysis of the radio link errors based on measurements in live Universal Mobile Telecommunication System (UMTS) radio access networks as well as new link error models originating from that analysis. It is shown that the knowledge of the specific link error characteristics leads to significant improvements in the quality of streamed video by applying the proposed novel network- and content-aware cross-layer scheduling algorithms. Although based on live UMTS network experience, many of the conclusions in this work are of general validity and are not limited to UMTS only.

• 한국항해항만학회지
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• 제30권5호
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• pp.363-367
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• 2006

전파천문학에 사용되는 전파망원경 및 수신기의 사용 주파수 대역은 가장 우수한 각 분해능을 제공하는 $10.5GHz\sim10.7GHz$이다. 위 기기들은 우주로부터 오는 미약한 신호를 수신해야 하므로 고성능 대역통과 필터의 개발이 요구되고 있다. 이에 본 논문에서는 전파천문학 기기용 대역통과 필터를 개발하였다. 사용 주파수대역이 $10.5GHz\sim10.7GHz$의 초극초단파 대역이므로 양호한 통과 특성과 대역 외에서의 불필요한 산호에 대한 억압 특성을 얻기 위해 마이크로스트립 선로를 이용하여 필터를 설계하였다. 설계된 대역통과 필터의 중심 주파수는 10.6 GHz로 하였으며, 통과 대역이 중심주파수의 5%인 대역통과 필터이다. ADS Tool을 이용한 시뮬레이션 결과를 토대로 제작한 대역통과 필터는 시뮬레이션으로 설계한 특성과 거의 일치하였기 때문에 제작된 대역통과 필터는 전파천문학 기기용 대역통과 필터로서 적합하다고 판단된다.

• 한국전자통신학회논문지
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• 제18권6호
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• pp.1337-1344
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• 2023

고주파 전기 수술 장비와 함께 사용되는 수중 치료용 고주파 전극 프로브에 대한 성능 평가 및 신뢰성 평가에 대한 안전성을 확보에 필요한 고주파 전극 프로브 개발 및 평가 시험방법 개발, 평가 모의시험 장치 개발하여 성능 안전성 확보에 필요한 성능 평가 효과를 알아보고자 한다.

• 천문학회지
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• 제46권2호
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• pp.65-74
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• 2013

We probe the feasibility of high-frequency radio observations of very rapid flux variations in compact active galactic nuclei (AGN). Our study assumes observations at 230GHz with a small 6-meter class observatory, using the SNU Radio Astronomical Observatory (SRAO) as an example. We find that 33 radio-bright sources are observable with signal-to-noise ratios larger than ten. We derive statistical detection limits via exhaustive Monte Carlo simulations assuming (a) periodic, and (b) episodic flaring flux variations on time-scales as small as tens of minutes. We conclude that a wide range of flux variations is observable. This makes high-frequency radio observations-even with small observatories-a powerful probe of AGN intra-day variability; especially, those which complement observations at lower radio frequencies with larger observatories like the Korean VLBI Network (KVN).

• 천문학회보
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• 제38권1호
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• pp.44.2-44.2
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• 2013

We probe the feasibility of high-frequency radio observations of very rapid flux variations in compact active galactic nuclei (AGN). Our study assumes observations at 230 GHz with a small 6-meter class observatory, using the SNU Radio Astronomical Observatory (SRAO) as example. We find that 33 radio-bright sources are observable with signal-to-noise ratios larger than ten. We derive statistical detection limits via exhaustive Monte Carlo simulations assuming (a) periodic, and (b) episodic flaring flux variations on time-scales as small as tens of minutes. We conclude that a wide range of flux variations is observable. This makes high-frequency radio observations - even with small observatories - a powerful probe of AGN intra-day variability; especially, those observations complement observations at lower radio frequencies with larger observatories like the Korean VLBI Network (KVN).

• Carbon letters
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• 제13권1호
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• pp.17-22
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• 2012

Currently, graphene is a topic of very active research in fields from science to potential applications. For various radio-frequency (RF) circuit applications including low-noise amplifiers, the unique ambipolar nature of graphene field-effect transistors can be utilized for high-performance frequency multipliers, mixers and high-speed radiometers. Potential integration of graphene on Silicon substrates with complementary metal-oxide-semiconductor compatibility would also benefit future RF systems. The future success of the RF circuit applications depends on vertical and lateral scaling of graphene metal-oxide-semiconductor field-effect transistors to minimize parasitics and improve gate modulation efficiency in the channel. In this paper, we highlight recent progress in graphene materials, devices, and circuits for RF applications. For passive RF applications, we show its transparent electromagnetic shielding in Ku-band and transparent antenna, where its success depends on quality of materials. We also attempt to discuss future applications and challenges of graphene.