• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.10 no.11
• /
• pp.1934-1939
• /
• 2006

Current digital communication system is selecting very various digital Modulation way. Need linear power amplifier necessarily to reduce interference for contiguity channel maximum in this communication system and at the same time, power amplifier of high efficiency is required. In this paper Compare with result of equilibrium power amplifier that design Doherty power amplifier of way that linearity and efficiency are improved at the same time through simulation optimization techniques and at the same time design through simulation, efficiency 20% linearity showed 10dB that is improved.

• Journal of the Institute of Electronics Engineers of Korea TC
• /
• v.39 no.9
• /
• pp.44-50
• /
• 2002

Recently, a envelope tracking(ET) amplifier that improves efficiency by changing of the bias according to the RF input level is presented to use for a high power amplifier of cellular radio handset using CDMA. The input and the output impedances of the ET amplifier may be varied by changing of the bias of the amplifier, and it makes the amplifier having low gain, low efficiency, and high input and output VSWR. In order to improve the input and the output mismatch of the amplifier, in this paper, two types of ET amplifier are suggested. In case of an ET amplifier using varactor diode, in experimentation, gain is improved about 7dB and the power consumption of the amplifier is better about 60% than that of the conventional amplifier. In case of a base voltage controlled ET amplifier, the gain and power consumption of the amplifier is improved about 9dB and 40% than those of the conventional amplifier, respectively.

• Journal of Korea Port Economic Association
• /
• v.37 no.4
• /
• pp.51-70
• /
• 2021

This study measured the environmental efficiency of 21 international airports based on sustainability reports issued by each airport for 2018. As many sectors in the industry paid attention to social and environmental responsibilities, airport operators comprise one of the leading sectors that streamlined their facilities to become increasingly sustainable and environmental. Nevertheless, studies on the environmental operations of airports are insufficient compared with studies on economic or operational efficiency. Therefore, the current study aims to determine any possible improvement in the environmental inefficiency of airports with the utilization of directional distance function (DDF) and to examine operational efficiency with the application of the data envelopment analysis (DEA). The majority of airports have operated their facilities efficiently, but not all have effectively managed pollutants generated by airports. Furthermore, many airports can still potentially reduce CO₂ and water consumption. This study suggests several implementable environmental improvements to the aviation sector. Moreover, other industrial sectors may use the research as a benchmark for enhancing environmental efficiency.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2011.02a
• /
• pp.382-382
• /
• 2011

보다 저렴한 다결정 실리콘 웨이퍼를 사용한 다결정 실리콘 태양전지의 발전효율개선을 위해서는 태양광스펙트럼의 표면 흡수기구를 최적화하고, 전자-정공쌍의 생성극대화 및 재결합 기구 제어를 통한 전하운바자들의 안정적인 분리와 전극으로의 효율적인 수집이 필수적인다. 현재 양질의 다결정 실리콘 웨이퍼에 기반한 다결정 실리콘 태양전지 양산공정에서 16~17% 발전효율이 이루어지고 있으며 18% 이상의 발전효율을 얻기 위해서는 보다 더 우수한 품질의 다결정 실리콘 웨이퍼가 요구된다. 본 연구에서는 15.5~16.5% 대역의 평균 발전효율을 갖는 15.6 cm${\times}$15.6 cm 크기 고효율 다결정 실리콘 태양전지 전면의 전자발광(EL : electroluminescence)데이터로부터 효율기여도가 높은 위치와 상대적으로 기여도가 낮은 위치들을 선정하여 380~1050nm 파장대역의 광선속에 대해 국부적인 외부양자효율(EQE : external quantum efficiency)을 측정하고 투과전자현미경(TEM : tunneling electron microscope) 등을 활용하여 결정방향 등에 기인하는 양자효율 악화기구를 분석하였다. 결론적으로 15%대의 상대적으로 낮은 발전효율을 보이는 태양전지들은 300~600 nm 단파장 영역에서 양자효율이 상대적으로 낮은 저급한 결정성의 웨이퍼에 기인하고 16.5%이상의 높은 발전효율을 갖는 태양전지들은 단파장영역에서 높은 양자효율을 갖는 영역이 수광면적의 80~90%를 차지하는 것으로 밝혀졌다. 이와 더불어 15%대의 발전효율을 갖는 태양전지에서는 600~1100 nm 파장대역에서 상대적으로 악화된 양자효율을 갖는 저급한 결정성 영역이 30~40%를 차지하였으나 16.5%대역의 고효율 태양전지에서는 저급한 결정성 영역이 5~10%를 차지하여 대조를 보였다. 따라서 18%이상의 높은 발전효율을 갖는 다결정 실리콘 태양전지의 양산을 위해서는 양자효율이 우수한 양품의 웨이퍼를 기반으로 표면 texturing을 통해 평균 태양광 흡수율을 90%이상으로 개선하고, 보다 미세한 프론트 전극패턴을 통해 수광면적을 개선하고 선택적인 에미티공정 기술 등을 적용할 필요가 있음을 제안하고자 한다.

• Proceedings of the KIEE Conference
• /
• 2011.07a
• /
• pp.1165-1166
• /
• 2011

본 논문에서는 대용량의 계통연계형 태양광발전시스템의 효율 개선을 위한 제어 알고리즘을 제안한다. 제안된 알고리즘은 태양전지로부터 생산되는 전체 전력량을 모니터링 하여 최대 효율 조건에서 동작할 수 있도록 구동시킬 인버터 수와 각 인버터가 담당할 전력량을 결정하고 이에 따른 태양전지의 직병렬 결합 조건이 가능하도록 태양전지의 배열을 릴레이 접점으로 재구성하는 방식이다. 제안된 알고리즘의 타당성 검증을 위해 LabVIEW 기반의 제어시스템을 구성하고 분석한다.

• Proceedings of the IEEK Conference
• /
• 2000.06b
• /
• pp.48-51
• /
• 2000

We proposed the new driving waveform which has changed the waveform of sustain division to improve luminous efficiency in plasma display panel. This sustain waveform is to add the ramp to the rectangular waveform, resulting in self-erasing discharge in the falling edge region. The proposed waveform has improved the luminous efficiency of 30％ even in low driving frequency(25kHz), whereas the conventional driving waveform using the self-erasing discharge can improve the luminous efficiency only in high driving frequency( >150kHz). Front the results of this paper, we hope that the variety study on frequency and duty ratio, ramp waveform will increase the luminous efficiency.

• The Journal of the Korea institute of electronic communication sciences
• /
• v.7 no.5
• /
• pp.983-989
• /
• 2012

IEEE 802.3az LPI mechanism allows an Ethernet link to reduce power consumption by entering a low-power sleeping mode and letting some components being powered off when there is no data to be transmitted through the link. However, if small amount of packets are being sent periodically, such a mechanism can not obtain energy efficiency due to a high overhead caused by excessive mode transitions. In this paper, we propose an enhanced LPI mechanism which can perform state transition adaptively based on the traffic characteristics on transport layer and network status. This simulation result shows that proposed mechanism improves energy efficiency than LPI mechanism with respect to energy consumption rate for various traffic loads.

• Journal of Advanced Marine Engineering and Technology
• /
• v.40 no.4
• /
• pp.348-352
• /
• 2016

This paper addresses the efficient improvement of the Switched Reluctance Motor(SRM) by the proper voltage excitation. In the case of loads with large operational motor-speed differences such as washing machine, an SRM system driven by a constant DC-link voltage is not useful for improving the efficiency. To reduce the effect of the excess DC-link voltage, AC-DC control converter that uses a silicon controlled rectifier instead of diode rectifier is employed in the SRM driver system. AC-DC control converter supplies a proper link voltage for low-speed operation. The experimental results demonstrated that the efficiency of the system was improved at low speeds.

• Journal of IKEEE
• /
• v.3 no.2 s.5
• /
• pp.215-220
• /
• 1999

In fabricated linear power amplifier(LPA), the third-order inter-modulation distortion(IMD) for main amplifier alone is 10.61dBc, and the IMD for LPA with predistorter and feedforward loop combined is 32.50dBc. Therefore, the IMD characteristic results an improvement of approximately 22dB. The main amplifier efficiency with single tone input is close to 30%, and the efficiency of the overall LPA with predistorter is 27.4% and predicted feedforward loop efficiency without predistorter is about 20%. Therefore, LPA with predistorter and feedforward loop combined is improved by 7.4%.

• Korean Journal of Remote Sensing
• /
• v.37 no.6_3
• /
• pp.2001-2010
• /
• 2021

The purpose of this study is to efficiently improve orthorectification of KOMPSAT images. As the development of domestic and abroad earth observation satellites accelerates, the number and amounts of satellite images acquired are rapidly increasing. Accordingly, various studies are being conducted to improve orthorectification for the acquired image more quickly and efficiently. This study focused on enhancing processing efficiency through algorithm improvement, except for improving hardware computing capabilities such as GPU. Accordingly, the algorithm was improved with the LUT-based RFM method, and compared and analyzed in terms of accuracy and time-efficiency that vary depending on offset settings.