共查询到18条相似文献,搜索用时 49 毫秒
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现有的非平稳信号分析方法都有各自不同的缺陷,短时傅里叶变换的时频分辨率受不确定性原理的限制,希尔伯特黄变换存在端点效应和模态混叠,易导致模糊的时频分布;解析模态分解只适合分析频率恒定的多分量信号;针对包含多个时变模态、特别是频谱重叠的非平稳信号,本文提出了一种新的信号分析方法———广义解析模态分解(Generalized Analytical Mode Decomposition,GAMD).GAMD通过广义傅里叶变换将时变频率转换为频谱可分的,采用解析模态分解对其分解,再对得到的单分量信号进行逆广义傅里叶变换即可得到原始信号的分量.因此,GAMD非常适合分析时变的非平稳信号.通过仿真信号将GAMD与短时傅里叶变换和希尔伯特黄变换等方法进行了对比,结果表明GAMD方法的分解效果更精确,时频分辨率更高. 相似文献
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非平稳信号的快速傅里叶变换与小波分析的比较 总被引:5,自引:0,他引:5
在对通信系统信号进行分析时,非平稳信号是经常遇到的。采用快速傅里叶变换和小波变换对通信系统信号进行分析,比较了分析结果,证明小波分析更适合于突发信号的分析。最后给出了Matlab实验结果。 相似文献
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通过傅里叶变换得到的频谱能够反映信号所包含的频率成分,但无法揭示瞬时频率随时间的变化特性。为满足工程应用中大量非平稳信号的分析需求,能够同时描述信号时域和频域特征的时频分析方法得到了广泛关注和深入研究。然而,传统时频分析方法所得到的时频分布往往具有较低的能量聚集性和较强的交叉项干扰,难以支撑信号时频特征的准确表达和提取。通过对信号内在稀疏特性进行挖掘和利用,能够有效提升信号时频分布的质量。本文通过对信号的相位函数进行泰勒展开,阐述了信号稀疏时频分解的实质,并分析了现有稀疏类时频分析的方法不足。在此基础上,提出了一种基于自适应短时Chirplet分解的高性能时频分布重构方法。首先,利用与信号时频特性自适应的窗函数为每一时刻生成了具有最强拟平稳性的最优短时信号;其次,提出了一种Chirplet字典的简化设计方法,利用得到的Chirplet字典对上述短时信号进行稀疏分解,基于分解结果实现了短时信号中心时刻瞬时频谱的参数化重构;最后,按时间顺序排列所有时刻的瞬时频谱,得到了信号能量聚集性高且不含任何交叉项干扰的高性能时频分布。仿真实验表明,所提方法有效改善了传统稀疏类时频分析方法结果中时频曲线... 相似文献
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该文首次在多天线多信道802.11无线网状网中提出了时频信道的概念。时频信道是通过在时间和频率两个维度划分无线资源取得的。这种划分方法增加了信道数量,使信道划分更加精细,为提高系统的信道利用率做了准备。在时频信道的基础上,提出了准动态信道分配算法。该算法可以和现有的固定信道分配算法结合,实现准动态信道分配,根据链路上负载变化,取得最大的吞吐量。该算法先根据固定信道分配算法为各链路分配相同数量的时频信道,剩余部分当作公共信道。在通信过程中,各链路首先使用分配给自己的信道和空闲的公共信道。如果分配给一个链路的信道不够,且别的链路上的信道有空闲,该链路还可以暂时使用这些空闲信道。理论分析和仿真结果证明该算法可以有效提高系统的吞吐量。 相似文献
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姜小磊 《电气电子教学学报》2007,29(5):27-32
众所周知,在时域(频域)离散化对应于在频域(时域)周期化,本文把采样和卷绕分别作为离散化和周期化的方式,考察在时域(频域)中相对应的混叠和内积。在这个统一的框架内,四类傅里叶表示被轮流使用,展示了微妙的联系。此外,得到这些结果的推导方法很容易从一种傅里叶表示移植到另一种傅里叶表示,所以易于为学生接受。 相似文献
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Li-Ming Zhang 《中国电子科技》2014,(2):201-205
The attempt to represent a signal simultaneously in time and frequency domains is full of challenges.The recently proposed adaptive Fourier decomposition(AFD)offers a practical approach to solve this problem.This paper presents the principles of the AFD based time-frequency analysis in three aspects:instantaneous frequency analysis,frequency spectrum analysis,and the spectrogram analysis.An experiment is conducted and compared with the Fourier transform in convergence rate and short-time Fourier transform in time-frequency distribution.The proposed approach performs better than both the Fourier transform and short-time Fourier transform. 相似文献
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自适应径向巴特沃思核时频表示 总被引:3,自引:0,他引:3
二次时频表示的性能由其核函数决定,一种固定的核只能适应于某些类型的信号,由此出现了核可随时间与信号变化的自适应核时频表示。本文采用径向为巴特沃思滤波器形式的核构造了一种自适应核时频表示。实验结果表明,对于不同类型的信号它都有好的性能。 相似文献
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Behdis Eslamnour S. Jagannathan Maciej J. Zawodniok 《International Journal of Wireless Information Networks》2011,18(4):295-308
Single-channel based wireless networks have limited bandwidth and throughput and the bandwidth utilization decreases with
increased number of users. To mitigate this problem, simultaneous transmission on multiple channels is considered as an option.
In this paper, we propose a distributed dynamic channel allocation scheme using adaptive learning automata for wireless networks
whose nodes are equipped with single-radio interfaces. The proposed scheme, Adaptive Pursuit learning automata runs periodically
on the nodes, and adaptively finds the suitable channel allocation in order to attain a desired performance. A novel performance
index, which takes into account the throughput and the energy consumption, is considered. The proposed learning scheme adapts
the probabilities of selecting each channel as a function of the error in the performance index at each step. The extensive
simulation results in static and mobile environments provide that the proposed channel allocation schemes in the multiple
channel wireless networks significantly improves the throughput, drop rate, energy consumption per packet and fairness index—compared
to the 802.11 single-channel, and 802.11 with randomly allocated multiple channels. Also, it was demonstrated that the Adaptive
Pursuit Reward-Only (PRO) scheme guarantees updating the probability of the channel selection for all the links—even the links
whose current channel allocations do not provide a satisfactory performance—thereby reducing the frequent channel switching
of the links that cannot achieve the desired performance. 相似文献
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综合特征值分解及Wigner分布时频遮隔提出了一种信号分解算法,并推广应用于其他交叉项抑制时频表示.对于由时频面上互不重叠分量合成的多分量信号,证明了信号分量可与各分量Wigner分布之和的逆Fourier变换的特征值分解相对应;通过阈值法可从抑制交叉项时频表示获得信号时频支撑区域,以此为模板遮隔Wigner分布可减少交叉项并保持自项聚集性,其逆Fourier变换的特征值分解就可实现多分量信号分解.仿真实例分析结果表明了该理论与算法的正确性和实用性.最后分析了算法性能并拓展了其实用范围. 相似文献
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From the channel assignment schemes in time division multiple access (TDMA) slot assignment protocols developed in previous
studies, we have found that these protocols do not have a convenient frame length reduction scheme after the expansion of
the frame length. As the network size grows, the frame length expands rapidly, particularly when we set it as a power of two.
A very long frame may result in poor channel utilization when it contains many unused slots. In this paper, we consider a
wireless mesh network with a TDMA structure. We divide each code into time slots to form the channels. We propose a dynamic
frame length expansion and recovery method termed adaptive distributed channel assignment (ADCA). This strategy is designed
to enhance the utilization of the available channels by taking advantage of the spatial reuse concept. In ADCA, an increase
in spatial reuse is achieved by adding a certain amount of control overhead. We show that the bandwidth saved due to the channel
spatial reuse is larger than the additional bandwidth spent on the control overhead.
相似文献
Yi-Yuan WangEmail: |
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In this paper, a study of adaptive lattice algorithms as applied to channel equalization is presented. The orthogonalization properties of the lattice algorithms make them appear promising for equalizing channels which exhibit heavy amplitude distortion. Furthermore, unlike the majority of other orthogonalization algorithms, the number of operations per update for the adaptive lattice equalizers is linear with respect to the number of equalizer taps. 相似文献