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频谱非对称包络调制的圆对称艾里光束的传播特性研究
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作者 宁啸坤 耿滔 《物理学报》 SCIE EI CAS CSCD 北大核心 2022年第10期81-90,共10页
为了增强圆对称艾里光束的自聚焦能力,本文使用了非对称双曲正割函数对光束的频谱进行了包络调制研究,详细探讨了频谱中高、低频分量对自聚焦特性的影响.结果表明单纯增加频谱的高频分量,并不会使自聚焦能力持续增强,低频分量对光束的... 为了增强圆对称艾里光束的自聚焦能力,本文使用了非对称双曲正割函数对光束的频谱进行了包络调制研究,详细探讨了频谱中高、低频分量对自聚焦特性的影响.结果表明单纯增加频谱的高频分量,并不会使自聚焦能力持续增强,低频分量对光束的自聚焦特性同样起着不可或缺的作用.由于非对称包络可以灵活的调节高、低频分量的比重,因此调制效果要优于高通滤波和对称包络调制.当调制参数选取适当时,光束焦点峰值大幅增加,达到了调制前的3.4倍,同时焦斑尺寸减小了23.6%.最后,本文对理论分析结果进行了实验验证,实验结果与理论结果相吻合,证明了频谱的非对称包络调制是一种高效且易于实现的调制方法. 展开更多
关键词 对称艾里光束 突然自聚焦光束 非对称包络 空间频谱
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Asymmetric Dual-Channel MAC Protocol for Multihop Mobile Ad Hoc Networks
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作者 Liu Kai Wang Dongdong +1 位作者 Liu Feng Wang Xin 《China Communications》 SCIE CSCD 2012年第8期52-63,共12页
In order to resolve the hidden and exposed terminal problems and improve the probability of concurrent packet transmissions for multihop Mobile Ad Hoc Networks (MANETs), a novel slotted Asyrmaetric Dual-Channel Medi... In order to resolve the hidden and exposed terminal problems and improve the probability of concurrent packet transmissions for multihop Mobile Ad Hoc Networks (MANETs), a novel slotted Asyrmaetric Dual-Channel Medium Access Control (ADC-MAC) protocol is proposed. It exploits sirmltaneous reservation with less collisions and conision-flee data packet transmissions, and achieves optimal transmission balance on the Control Channel (CCH) and Data Channel (DCH) by adjusting the relationship between Reservation Slot (RS) on the CCH and the data packet Transmission Slot (TS) on the DCH. Transmission interferences can be avoided by only observing CCH for the transmission time of a data packet. The proposed RS and contention micro-slot backoff mechanisms also greatly improve channel access efficiency. Simulation results show that compared to IFEE 802. 11 DCF and -Mc protocols, the proposed protocol can achieve a throughput gain of 88% in singlehop networks and 151% in nltihop networks at the same total data rate. 展开更多
关键词 mobile ad hoc networks medium access control asyrrcnetric dual-channel RESERVATION collision avoidance nltichannel hidden and exposed terminal problerm
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