共查询到18条相似文献,搜索用时 123 毫秒
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一、信号的频谱连续信号有周期与非周期之分,周期信号采用频谱,非周期信号采用频谱密度.但习惯上统称为频谱.若周期为T的周期信号记为f_T(t),其频谱(指数形 相似文献
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一种抗混叠的非均匀周期采样及其频谱分析方法 总被引:3,自引:0,他引:3
非均匀采样可以突破采样定理的限制,但非均匀采样信号的频谱在所有频率段均存在混叠频谱噪声,这些频谱噪声会淹没真实信号中的一些频谱幅度较小的信号,使得非均匀采样无法检测小信号。本文提出一种非均匀周期采样方法,该方法既具有非均匀采样抗混叠的特性,又具有均匀采样的消除混叠频谱噪声的特点。文中详细分析了非均匀采样产生混叠频谱噪声的原因,提出了基于非均匀周期采样的傅里叶变换方法,并给出了实验结果。理论和实验表明,非均匀周期采样方法是一种行之有效的采样方法。 相似文献
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扩频通信的频谱相关检测方法 总被引:9,自引:0,他引:9
基于周期平稳信号特征和频谱相关密度,本文提出了利用频谱相关处理检测扩频通信信号的频谱相关检测方法。这种方法的检测性能常规经典方法,并有更好的抗噪声和干扰的能力。 相似文献
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针对电子战操作员通过观察最大保持频谱变化来发现重要频率信号的需要,提出了一种基于最大保持频谱提取天线扫描周期的自相关处理方法。针对实测频谱数据的四种典型形态,利用自相关函数的周期性完成了对固定频率机械扫描雷达的天线扫描周期提取,实验表明该算法可用于多目标和噪声信号混叠的场景,并在实际多组频谱样本数据测试中达到了平均80%的准确率,可以帮助操作员发现感兴趣频率信号。 相似文献
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基于周期平稳信号特征和频谱相关密度,本文提出了利用频谱相关处理提取大频偏低信噪比扩频通信信号的载波频率的频谱相关检测方法.这种方法的检测性能优于常规经典方法,并有更好的抗噪声和干扰的能力. 相似文献
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试论非均匀取样周期信号的数字频谱 总被引:8,自引:3,他引:5
在许多高速数据采集系统中,由于取样时基抖动等因素影响,取样过程实际上是非均匀的。本文首先介绍这类非均匀取样模型及数字频谱分析的一般原理,然后详细地导出了非均匀取样周期信号的数字频谱表达式,讨论了它们的一些重要特性;最后分析了四种典型的非均匀取样现象,得出了估计非均匀取样周期信号信噪比(S/N)的一般公式及若干结论。本文的思想和有关结论对开展非均匀时间序列分析、谱估计理论研究及高速数据采集系统的设计都有明显价值。 相似文献
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相频谱在频谱分析中占有重要地位,它包含了信号的大量信息。相频谱计算是"测试技术"课程教学中的难点,但教科书中对相频谱重视不够,这给教学造成了较大困难。本文在介绍初相位概念的基础上,系统总结了周期信号相频谱求解中的主要问题,并提出了一些建议,以弥补现有教材中这部分内容的不足。 相似文献
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对多路 A/D采样过程中出现的一类非均匀、非理想采样信号进行了频谱分析 ,得到了此类信号的数字谱表达形式 ,并对非均匀采样周期信号的数字谱进行了深入的研究 ,得到了其数字谱完整的表达形式及其一些重要性质。 相似文献
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M. P. Slichenko 《Journal of Communications Technology and Electronics》2014,59(10):1069-1075
A closed-form analytic representation of multidimensional periodic functions with a finite Fourier spectrum is obtained as a modified interpolation series with a finite number of terms. The corresponding theorem is formulated, and the multidimensional periodic kernel of the expansion is analyzed. It is shown that such a representation makes it possible to calculate values of the derivatives of an arbitrary order of a periodic function with a finite spectrum from the samples of this function. 相似文献
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Sampling theory for continuous time signals which have a bandlimited representation in fractional Fourier transform (FrFT) domain-a transformation which generalizes the conventional Fourier transform-has blossomed in the recent past. The mechanistic principles behind Shannon's sampling theorem for fractional bandlimited (or fractional Fourier bandlimited) signals are the same as for the Fourier domain case i.e. sampling (and reconstruction) in FrFT domain can be seen as an orthogonal projection of a signal onto a subspace of fractional bandlimited signals. As neat as this extension of Shannon's framework is, it inherits the same fundamental limitation that is prevalent in the Fourier regime-what happens if the signals have singularities in the time domain (or the signal has a nonbandlimited spectrum)? In this paper, we propose a uniform sampling and reconstruction scheme for a class of signals which are nonbandlimited in FrFT sense. Specifically, we assume that samples of a smoothed version of a periodic stream of Diracs (which is sparse in time-domain) are accessible. In its parametric form, this signal has a finite number of degrees of freedom per unit time. Based on the representation of this signal in FrFT domain, we derive conditions under which exact recovery of parameters of the signal is possible. Knowledge of these parameters leads to exact reconstruction of the original signal. 相似文献
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A new wavelet representation is explored. The transform is based on a pitch-synchronous vector representation and it adapts to the oscillatory or aperiodic characteristics of signals. Pseudo-periodic signals are represented in terms of an asymptotically periodic trend and aperiodic fluctuations at several scales. The transform reverts to the ordinary wavelet transform over totally aperiodic signal segments. The pitch-synchronous wavelet transform is particularly suitable to the analysis, rate-reduction coding and synthesis of speech signals and it may serve as a preprocessing block in automatic speech recognition systems. Feature extraction such as separation of voice from noise in voiced consonants is easily performed by means of partial wavelet expansions. A stochastic model of aperiodic fluctuations is proposed 相似文献
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飞机发动机旋转叶片引起的周期性运动部件调制(PMPM)影响目标多普勒频率跟踪精度,同时也为目标识别提供了重要特征信息。该文基于旋转叶片组电磁散射计算模型和实验测量数据,重点分析了PMPM频谱包络调制现象的形成原因。结果表明:与叶片倾斜角一样,扭角也是影响PMPM频谱分布的重要因素。 相似文献