共查询到18条相似文献,搜索用时 500 毫秒
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利用时频分析方法估计信号瞬时频率,在低信噪比条件下估计性能较差,但在时频图中,信号频率的变化趋势具有一定的规律,基本上都是围绕着信号的真实频率。基于此,给出了一种结合时频分析和信号频率模型相结合的方法,以实现信号瞬时频率的高精度估计。利用时频分析具有的良好时频分布的特点,采用最大能量方法(ME)预先估计得到信号的预估计瞬时频率(EIF);再利用瞬时频率连续性、平滑性的先验信息,建立了信号瞬时频率估计模型,并采用概率最大原理(MP)估计瞬时频率概率最大的统计变化,估计得到预估计瞬时频率的滤波起始点;最后利用卡尔曼滤波和平滑算法对预估计瞬时频率进行滤波和平滑,从而得到信号频率的精确估计。 相似文献
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将双向高斯核函数时频分布引入到非平稳信号瞬时频率估计。通过控制时延、频移参数,该时频分布能够有效提高时频分辨率,同时对多分量信号检测时存在的交叉项能够得到很好的抑制。理论推导及计算机仿真均表明该分布具有良好的性能。 相似文献
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瞬时频率估计(Instantaneous Frequency, IF)在雷达信号处理中有着重要的研究意义,时频分布峰值检测是IF估计研究和应用中较为普遍和有效的方法,但由于噪声的影响,时频分布峰值往往偏离真实的IF曲线。针对低信噪比下的IF估计,文中首先对WVD及CWD的时频分布矩阵作Hadamard积,得到一种混合的时频分析方法,而后采用多样本信号时频能量累乘的方法,进一步抑制噪声在时频面上的分布;然后以时频分布峰值在信号自项时频聚集区域的分布概率为准则,计算出时频分布的数据窗长,并根据该窗长得到IF的初始估计;最后依据初始IF,采用交叉置信区间算法对时频分布峰值进行检测,得到信号的瞬时频率估计值。文中对NLFM、LFM和FSK信号的IF估计进行了研究,并与WVD峰值检测法和时频分布一阶矩法进行了比较,仿真结果表明了本文方法的有效性。 相似文献
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瞬时频率(Instantaneous Frequency,IF)估计在多分量信号处理中具有重要意义,而现有方法在信号分量的IF曲线相近或相交时估计准确度不佳。针对这一问题,本文提出一种基于条件对抗生成时频分布的多分量信号IF估计方法。该方法首先采用时频分析产生信号的时频图像(例如掩膜维格纳分布)作为条件生成对抗网络(Conditional Generative Adversarial Networks, CGAN)的原始数据集,通过训练CGAN进行学习之后生成接近理想时频分布的时频图像。根据这些图像,本文利用一种改进的维特比算法提取出不同分量的IF曲线。其改进点在于增加了一个线段梯度的惩罚项,使维特比算法在分量相交的时频区域仍有准确的IF估计。实验结果表明,该方法能够有效且准确地估计分量相近或相交情况下信号的IF信息。 相似文献
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微多普勒特征提取的关键在于瞬时频率的计算,峰值检测法和一阶时间条件矩法是基于高分辨时频分布的两种瞬时频率估计算法.本文对两种瞬时频率估计算法对噪声的适应性能进行了理论分析和仿真计算,结果表明,当信号受噪声污染后,在一定的信噪比条件下,峰值检测法瞬时频率估计算法对能量分布的变化不敏感,但一阶时间条件矩法瞬时频率估计算法对时频域能量分布十分敏感,因此,峰值检测法较一阶时间条件矩法对噪声具有鲁棒性.实际中雷达接收到的信号都是受噪声污染的,分析两种算法对噪声的适应性能对工程实际应用具有重要参考价值. 相似文献
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提出了一种新的基于时频分布的相位误差估计方法。相位误差的存在严重影响着合成孔径雷达(SAR)成像的质量,综合利用信号的不同时频分布的互补优势,获取具有强健于噪声且具有较高时频分辨率的时频分布图,在此基础上,利用曲线拟合获得瞬时频率进而获得相位误差的较高精度估计。实验结果表明,该方法简单易行,且具有较好的相位误差估计效果。 相似文献
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We describe an approach to time-frequency analysis based on the local approximation of the signal by a first order Taylor series. We show that the Taylor approximation provides a representation of the signal in terms of its instantaneous frequency and instantaneous bandwidth. This representation can be translated into the frequency domain in a straightforward manner. The key to this approach is the local decomposition of the signal into its components, which is similar to the problem of estimating the parameters of of complex exponentials from observation of their sum. The resulting time-frequency representation (TFR) does not have the time and frequency marginal properties shared by many of the time-frequency distributions presented in the literature, but is additive over the signal components and, by its construction, does not have cross-terms. 相似文献
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Igor Djurovi? 《Signal processing》2011,91(5):1308-1314
An instance of the Viterbi algorithm has been applied to the cubic phase function and chirp-rate estimation. The proposed algorithm has shown excellent performance for high noise environment. The obtained chirp-rate estimate is used in the instantaneous frequency estimation. The proposed instantaneous frequency estimator gives superior performance with respect to the state-of-the-art techniques for signals with non-linear instantaneous frequency. 相似文献
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According to the performance degradation problem of the carrier frequency estimation method of time-frequency overlapped BPSK signals in Alpha-stable distribution noise,a novel carrier frequency estimation algorithm of the time-frequency overlapped BPSK signals based on the cyclic correntropy spectrum was proposed.The relationship between cyclic frequency and carrier frequency on the zero frequency section of the cyclic correntropy spectrum was deduced,which could be utilized for carrier frequency estimation.The proposed method can suppress the impulse noise and has better estimation performance than that of the contrastive methods.Simulation results are presented to demonstrate the effectiveness and robustness of the proposed method. 相似文献
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This paper presents an analysis of the representation of instantaneous frequency using time-frequency distributions of energy density domain. Similarity to the “ideal” instantaneous frequency presentation is chosen as a criterion for comparison of various distributions. Although all the commonly used distributions suffer from the artifacts along frequency axis, it is shown that the Wigner distribution is the best among them, with respect to this criterion. The generalization of Wigner distribution-LWD-is introduced to decrease the artifacts. The properties of the LWD are analyzed. It is shown that, at the expense of an insignificant increase in computation time, much better results are obtained. The theory is illustrated by a numerical example with the frequency modulated signals 相似文献
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为了在α稳定分布噪声的环境下获得清晰的跳频信号时频图,提出一种基于分数低阶SPWVD(Smoothed Pseudo Wigner-Vile Distribution)与形态学滤波相结合的跳频信号时频图修正算法。首先,根据接收到的多跳频信号建立跳频信号的模型和α稳定分布噪声模型;然后,采用低阶SPWVD变换抑制时频图中脉冲噪声;最后,根据形态学滤波处理方法对残留噪声进一步抑制进而得到清晰时频图。理论分析和仿真结果表明,所提算法在广义信噪比为-5 dB时仍可以得到清晰可靠的跳频信号时频图,并且基于时频图的参数估计性能优良。 相似文献
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《Signal Processing, IEEE Transactions on》1991,39(3):755-756
The conditional moments of frequency of a time-frequency distribution are discussed, and it is shown that they may be related to the derivative of the log of the corresponding signal, a complex function whose imaginary part is the instantaneous frequency. For the complex energy spectrum, a general form for the moments is obtained. For a signal which is the sum of several other signals, the instantaneous frequency will always demonstrate erratic behavior 相似文献