• Journal of Communications and Networks
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• 제18권3호
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• pp.320-326
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• 2016

In existing literature on multiple-input multiple-output (MIMO) relaying communication systems, antenna selection is often implemented by maximizing the channel capacity or the output single-to-noise ratio (SNR). In this paper, we propose an energy-efficient low-complexity antenna selection scheme for MIMO relaying communication systems. The proposed algorithm is based on beamforming and maximizing the Frobenius norm to jointly optimize the transmit power, number of active antennas, and antenna subsets at the source, relaying and destination. We maximize the energy efficiency between the link of source to relay and the link of relay to destination to obtain the maximum energy efficiency of the system, subject to the SNR constraint. Compared to existing antenna selection methods forMIMO relaying communication systems, simulation results demonstrate that the proposed method can save more power in term of energy efficiency, while having lower computational complexity.

• Journal of information and communication convergence engineering
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• 제10권3호
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• pp.215-219
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• 2012

This paper applies transmit antenna selection algorithms to spatial-temporal combining-based spatial multiplexing (SM) ultra-wideband (UWB) systems. The employed criterion is based on the largest minimum output signal-to-noise ratio of the multiplexed streams. It is shown via simulations that the bit error rate (BER) performance of the SM UWB systems based on the two-dimensional Rake receiver is significantly improved by antenna diversity through transmit antenna selection on a log-normal multipath fading channel. When the transmit antenna diversity through antenna selection is exploited in the SM UWB systems, the BER performance of the spatial-temporal combining-based zero-forcing (ZF) receiver is also compared with that of the ZF detector followed by the Rake receiver.

• 한국통신학회논문지
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• 제25권5B호
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• pp.931-941
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• 2000

안테나 배열을 이용하는 직접 대역 확산 시스템에서 포착 가능한 SNR의 범위를 크게 낮출 수 있는 안테나 배열을 사용한 직렬 포착 방식을 제안한다. 제안된 포착 방식에서의 SNR 향상을 위하여, 안테나 요소마다 동일한 PN 위상을 갖도록 조정된 비동기 I-Q 정합 여파기들에서의 독립된 판정 변수들의 합을 초기 포착을 위한 판정 변수로 사용한다. 제안된 방식의 성능 분석을 위하여 가우시안 전송로와 Rayleigh 페이딩 전송로에서 검출확률과 오인확률이 유도되며, 이를 이용하여 평균 포착시간이 분석된다. 수치적 분석 결과를 통하여, 안테나 개수가 늘어남에 따라 제안된 방식의 포착 성능이 계속적으로 향상됨을 확인할 수 있다.

• ETRI Journal
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• 제33권6호
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• pp.849-856
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• 2011

This research introduces three new fractal array configurations that have superior performance over the well-known Sierpinski fractal array. These arrays are based on the fractal shapes Dragon, Twig, and a new shape which will be called Flap fractal. Their superiority comes from the low side lobe level and/or the wide angle between the main lobe and the side lobes, which improves the signal-to-intersymbol interference and signal-to-noise ratio. Their performance is compared to the known array configurations: uniform, random, and Sierpinski fractal arrays.

• 한국통신학회논문지
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• 제40권11호
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• pp.2298-2304
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• 2015

본 논문은 다중 셀 다중입력 단일 출력 (MISO : multiple-input single-output) 하향링크 능동 안테나 시스템 (AAS : active antenna systems)에서 기지국의 수직 각도를 최적화하는 새로운 기법을 제시한다. 본 연구에서는 기존의 전역 탐색 방식 대신 간단하면서 최적의 값에 근사한 알고리듬들을 제안한다. 먼저, random matrix theory의 특성을 반영하여 평균 전송용량에 large system approximation이 적용된 수직적 빔포밍 알고리듬을 소개한다. 다음으로, signal-to-leakage-and-noise ratio (SLNR)을 기반으로 최적화 문제를 간단하게 만드는 수직적 빔포밍 알고리듬을 제안한다. 실험 결과를 통해 제안된 알고리듬들의 성능이 기존의 전역 탐색 알고리듬에 비해 복잡도가 매우 감소됨에도 불구하고 거의 비슷한 성능을 보임을 증명하였다.

• 한국전기전자재료학회논문지
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• 제26권4호
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• pp.309-314
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• 2013

This paper dealt with the radiated electromagnetic wave detection of partial discharge (PD) in oil for insulation diagnostics of oil-immersed transformers. Three types of electrode system were fabricated to simulate the insulation defects that could occur in oil-immersed transformers. Frequency components of radiated electromagnetic wave in oil was measured by broadband bi-conical antennas of 300 MHz~2 GHz and a spectrum analyzer of 9 kHz~3 GHz. Frequency component of electromagnetic waves from PD in oil were highly distributed at 500 MHz. From the result, a narrow-band monopole antenna with the center frequency of 500 MHz was fabricated. We could detect PD signal in insulation oil without an influence of external noise by a measurement system which consists of the prototype monopole antenna, a LNA (Low Noise Amplifier), an oscilloscope and a spectrum analyzer.

• 한국측량학회:학술대회논문집
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• 한국측량학회 2004년도 춘계학술발표회논문집
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• pp.461-464
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• 2004

The Broadcasting system is very important part of human life that preceding to people news, national plan, sport, drama, leisure and politics. The product of maded by broadcasting system conveyed the whole country by radio signal. A broadcasting station operate the broadcast product radio trial network in the mountain, Recently the height of new building, concrete structure is very large and higher than old one. Since one does or says, noise accur to radio and TV signal whole nation. In this study, Taejeon Sikjang mountain and Cheunan-Heuksung mountain where accured radio noise chosen as a sample, and analysis 3D simulation and plane check. Accordingly come to conclusion condition of noise occurred radio antenna.

• 제어로봇시스템학회논문지
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• 제20권9호
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• pp.977-983
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• 2014

A repeat-back jamming signal is an intentionally re-broadcasted GNSS (Global Navigation Satellite System) interference. In this paper, a novel repeat-back jamming detection scheme is proposed. The proposed scheme uses a combined pseudo random noise signal (C-PRN) and is available for a generic GNSS receiver with a single antenna. The C-PRN signal is made by combining several received pseudo random noise signals that had been transmitted from the visible GNSS satellites. Through a Monte-Carlo simulation, the detection probability of a repeat-back jamming signal detected with the proposed scheme is presented.

• 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.

• 한국정보전자통신기술학회논문지
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• 제8권3호
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• pp.224-228
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• 2015

본 논문에서는 상관성 신호가 수신 시스템에 입사하는 경우 원하는 신호를 추정하는 방법에 대해서 연구한다. 안테나 수신 신호의 잡음과 간섭을 제거하고 원하는 신호를 추정하기 위해서 적응배열 안테나 시스템과 도래 방향 알고리즘의 부 공간 기법을 적용시킨다. 적응 배열 안테나의 배열 응답 벡터는 베이즈 방법을 이용하여 확률적으로 나타내고 신호의 가중치를 갱신하여 목표물의 도래 방향을 정확히 추정한다. 본 연구에서 원하는 신호의 추정 방법은 공분산 행렬의 가중치를 갱신하여 수신신호의 간섭과 잡음을 제거한 후 배열 응답벡터를 원하는 신호 공분산 행렬의 갱신 가중치에 적용한다. 부 공간 기법의 고유치 와 고유 분해를 이용하여 고 분해능 도래 방향 추정 알고리즘에서 신호 부 공간과 잡음 부 공간으로 구분하여 원하는 신호를 정확히 추정한다. 모의실험을 통해서 기존의 방법과 본 연구에서 제안한 방법을 비교 분석한다.