• Journal of the Institute of Electronics Engineers of Korea CI
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• v.44 no.3
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• pp.37-42
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• 2007

This paper reconsiders established power conservation models for ubiquitous sensor networks that use relay nodes instead of direct communication and proposes novel network power consumption model with consideration of the channel level and radio chip level simultaneously. We estimate the effect of minimum hop-count policy in terms of network power consumption through simulation of various situations for low power RF module CC2420. It is observed that maximum RF power and minimum hop-count results in lower energy consumption relatively. Also, in total network energy consumption, which is included re-transmission, minimum hop count policy presents decrease by 33.1% of energy consumption in compare with the conventional model.

• Information and Communications Magazine
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• v.29 no.11
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• pp.75-80
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• 2012

본고에서는 송신단과 수신단 사이에 접점 없이 높은 효율을 유지하면서 기존의 방식(전자기유도방식, 전자기파방식) 보다 실용적인 거리의 무선전력전송이 가능한 자기공명방식 무선전력전송 기술을 소개하고 이를 모바일 단말기용에 적용하기 위하여 고효율 송/수신단 회로 설계, 자기공명안테나 설계, 실시간 임피던스 매칭 기술, 실시간 전력제어 기술 등등의 구현을 위한 요소기술에 대하여 소개함으로써 자기공명방식이 가지고 있는 특성을 구체적으로 알아본다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38A no.8
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• pp.697-703
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• 2013

We propose an efficient frequency-time domain resource allocation scheme in multi-carrier (MC) direct-sequence code-division multiple-access (DS/CDMA) communications. We consider, as a power allocation strategy in the frequency domain, transmitting each user's DS waveforms over the user's sub-band with the largest channel gain. We then consider rate adaptation in the time domain, where the data rate is adapted such that a desired transmission quality is maintained. We analyze the achievable average data rate of the proposed scheme with fixed average transmission power, and compare the performance to single carrier DS/CDMA systems with power and rate adaptations.

• Journal of the Institute of Electronics and Information Engineers
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• v.51 no.9
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• pp.41-45
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• 2014

In this paper, a high-efficiency power amplifier is implemented by using a drain bias control circuit operated at low input power for WPT(Wireless Power Transfer). Adaptive bias control circuit was added to high-efficiency class-E amplifier. It was possible to obtain the overall improvement in efficiency by adjusting the drain bias at low input power. The proposed adaptive class-E amplifier is implemented by using the input and output matching network and serial resonant circuit for improvement in efficiency. Drain bias control circuit consists of a directional coupler, power detector, and operational amplifier for adjusting the drain bias according to the input power. The measured results show that output powers of 41.83 dBm were obtained at 13.56 MHz. At this frequency, we have obtained the power added efficiency(PAE) of 85.67 %. It was confirmed increase of PAE of an average of 8 % than the fixed bias from the low input power level of 0 dBm ~ 6 dBm.

• Journal of the Institute of Convergence Signal Processing
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• v.20 no.2
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• pp.111-117
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• 2019

We investigated the variations in the magnetic-field distribution and power transmission efficiency, resulting from changes in the relative positions of the transmitting and receiving coils, for electromagnetic-induction-type wireless power transmission using an elliptical receive coil. Results of simulations using a high-frequency structure simulator were compared to actual measurement results. The simulations showed that the transmission efficiency could be maintained relatively stable even if the alignment between the transmitting and receiving coils was changed to some extent. When the centre of the receiving coil was perfectly aligned with the centre of the transmitting coil, the transmission efficiency was the maximum; however, the degree of decrease in the transmission efficiency was small even if the centre of the receiving coil moved by ± 10mm from the centre of the transmitting coil. Therefore, it is expected that the performance of the wireless power transmission system will not be degraded significantly even if perfect alignment is not maintained. The results suggested a standardized application method of wireless transmission in the utilization of wireless power for implantable sensors.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.21 no.5
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• pp.1035-1041
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• 2017

In magnetic resonance-based wireless power transfer (WPT) systems, frequency splitting phenomenon, in which power transfer efficiency (PTE) decreases seriously as resonators are close to each other, is the problem that we should address for reliable power transfer in short distance. In this paper, we present WPT systems using an equivalent circuit model and analyze PTE and marginal coupling coefficient ($k_{split}$) where the frequency splitting occurs. In addition, we perform circuit-level simulations using Advanced Design System, and show that the achievable PTE is different for the structures of resonators when k>$k_{split}$. We confirm that higher PTE can be ensured as k increases in the case of identical resonators, while PTE is degraded as k increases in the case of non-identical resonators. Therefore, in short distance, in which k>$k_{split}$, it is more efficient for achieving reliable PTE to use identical resonators rather than non-identical resonators.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.26 no.6B
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• pp.717-726
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• 2001

감쇄를 겪는 무선 채널 환경에서 전력과 대역폭을 효율적으로 조절하여 데이터를 전송하는 적응 부호 변조 방식에 적합한 제어 기법을 제안한다. 먼저 부호화 시스템에 맞도록 평균 대역폭 효율을 다시 정의하였고, 이것에 기초하여 전력 및 대역폭 효율을 최대화하도록 변조 레벨 구간을 얻었다. 이 제어 기법은 부호 이득을 최대로 이용할 수 있고, 변조 형태에 관계없이 대역폭 효율을 최대화 할 수 있다. 모의 실험 결과 제안한 방식은 요구된 비트 오율 성능을 만족하면서 기존의 방식보다 전력 할당을 효과적으로 하기 때문에 대역폭 효율이 향상되었다. 본 논문에서 제안한 제어 기법은 감쇄 특성을 가진 무선 채널에서 고속 데이터 전송에 사용될 수 있다.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2001.11b
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• pp.121-126
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• 2001

본 논문에서는 절단 전력 제어를 사용하는 위성통신 시스템에서 부호율을 채널 상황에 따라 적응시켜 최대의 전송 효율을 얻는 하이브리드 ARQ 타입1 부호율 제어 기법을 제안한다. 제안된 기법의 성능을 분석하기 위하여 먼저 하이브리드 ARQ 타입 1 시스템에서 부호율을 채널 상황에 따라 적응적으로 제어했을 때의 전송 효율과 패킷 오율을 유도한다. 또한, 유도된 패킷 오율식으로부터 절단 전력 제어에서 필요한 목적 수신 SNR값을 사용되는 각 부호율에 대해 구하고, 전송 효율을 최대화하는 최적의 부호율 제어변수를 효율적으로 구할 수 있는 방식을 제안한다. 전송효율 측면에서 분석한 결과 제안된 방법이 기존의 방식에 비하여 우수한 성능을 보여줄 수 있음을 확인하였다.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.25 no.3
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• pp.304-310
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• 2014

This paper presents the analysis of the coupling coefficient(k), Q value of the resonator, and the optimum loaded resistance at Rx for the magnetically coupled wireless power transmission using two loops(resonators). In addition, the metamaterial, conductor, and the relay methods have been used in order to improve the limitation problem of transmission efficiency by using the figure of merit. We have achieved the increase of transmission efficiency about 11~60 % using the proposed methods by analyzing and comparing the results based on EM simulations.

• 전기의세계
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• v.46 no.12
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• pp.55-56
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• 1997

학문과 산업의 발전에 따라 전기공학의 전문연구분야가 활성적으로 연구되고 학술활동도 활발하게 진행됨에 따라 전문분과별 연구활동이 필요하게 되었으며, 효율적인 전기 에너지의 발생과 전송, 운용에 관한 전력기술의 발전과 이용보급을 위한 전력계통 연구회는 1975년 11월 1일 대전공업전문학교에서 창립되어 꾸준히 발전되어 왔다. 전력수송과 운요에 관련된 전력계통의 운용과 해석, 신전기에너지의 발생, 전송, 합리적인 이용, 대체에너지 등에 대한 연구활동을 하는 회원들로 구성된 연구회이며, 전력의 효율적이고 안정된 공급에 관련된 학문과 기술의 발달, 회원의 적극적인 연구참여로 산업의 근대화와 국민생활의 고도화에 기간을 이루는 전력계통의 발전에 크게 기여하는 성과를 거두었으며, 적극적인 연구와 학술활동을 하고 있다.