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91.
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前视阵高速雷达空时处理方法研究 总被引:1,自引:0,他引:1
多普勒严重模糊,训练样本有限是高速平台雷达面临的重要问题,协方差矩阵估计误差以及目标约束误差将使处理器性能严重下降。针对上述问题,该文对前视阵杂波自由度进行了研究,分析表明杂波特征谱与孔径带宽积、时宽带宽积以及空时耦合特性有关。该文提出基于主瓣区域空时多波束的鲁棒空时处理方法,首先通过空时多波束降低杂波自由度,然后利用多普勒区间约束的方法,提高了处理器的性能和系统鲁棒性。仿真实验证明了该文方法的有效性,当样本中存在目标信号时,该文方法相比传统固定约束矢量的方法输出信杂噪比性能平均提高5 dB左右。 相似文献
93.
针对激光多普勒信号中存在较大噪声干扰的实际情况,为了抑制这些噪声干扰,提高激光多普勒测速仪的测量精度,提出了对激光多普勒信号进行最小均方差(LMS)自适应滤波后作快速傅里叶变换(FFT),基于混合编程思想对所得到的频谱,先进行频谱细化,再进行频谱校正的信号处理方法,并对理想正弦信号和实测多普勒信号分别进行仿真计算和实验研究。仿真和实验结果表明:LMS自适应滤波技术可以有效抑制激光多普勒测量中的多频率噪声的干扰,此技术能够适应于很宽的信噪比范围,大大提高多普勒信号的信噪比;频谱细化技术可以提高激光多普勒信号的频谱分辨率,频谱校正技术可以准确地校正多普勒频率,使校正后的频率更加接近于真实值;信号处理精度比直接进行FFT提高2~3倍。 相似文献
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以Alpha稳定分布作为噪声模型,研究了脉冲噪声环境下宽带双基地MIMO雷达系统中参数估计问题.针对在脉冲噪声环境中,基于传统的信号模型和算法效果显著退化的问题,本文提出了基于分数低阶统计量的宽带模糊函数算法.首先根据分数低阶宽带模糊函数的峰值点实现对多普勒频率尺度因子和时延的联合估计.接下来基于分数低阶宽带模糊函数构造两个子阵.通过采用改进的MUSIC算法和ESPRIT算法实现了收发角的联合估计.仿真实验表明本文算法具有很好的性能. 相似文献
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In situ measurement on nonuniform velocity distributionin external detonation exhaust flow by analysis ofspectrum features using TDLAS 下载免费PDF全文
Instantaneous and precise velocity sensing is a critical part of research on detonation mechanism and flow evolution.This paper presents a novel multi-projection tunable diode laser absorption spectroscopy solution,to provide a real-time and reliable measurement of velocity distribution in detonation exhaust flow with obvious nonuniformity.Relations are established between overlapped spectrums along probing beams and Gauss velocity distribution phantom according to the frequency shifts and tiny variations in components of light-of-sight absorbance profiles at low frequencies analyzed by the fast Fourier transform.With simulated optical measurement using H2O feature at 7185.6 cm-1 carried out on a phantom generated using a simulation of two-phase detonation by a two-fluid model,this method demonstrates a satisfying performance on recovery of velocity distribution profiles in supersonic flow even with a noise equivalent absorbance up to 2×10-3.This method is applied to the analysis of rapidly decreasing velocity during a complete working cycle in the external flow field of an air-gasoline detonation tube operating at 25 Hz,and results show the velocity in the core flow field would be much larger than the arithmetic average from traditional tunable diode laser doppler velocimetry.This proposed velocity distribution sensor would reconstruct nonuniform velocity distribution of high-speed flow in low cost and simple operations,which broadens the possibility for applications in research on the formation and propagation of external flow filed of detonation tube. 相似文献
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Slobodan Djukanovi? Vesna Popovi?Miloš Dakovi? Ljubiša Stankovi? 《Signal processing》2011,91(6):1425-1431
The problem of non-stationary interference suppression in direct sequence spread-spectrum (DS-SS) systems is considered. The phase of interference is approximated by a polynomial within the considered interval. According to the local polynomial Fourier transform (LPFT) principle, the received signal is dechirped by using the obtained phase approximation and the interference is, in turn, suppressed by excising the corrupted low-pass frequency band. For the estimation of polynomial coefficients, we use the product high-order ambiguity function (PHAF), known for its capability to successfully resolve components of a multicomponent polynomial-phase signal (PPS). The proposed method can suppress interferences with both polynomial and non-polynomial phase. In addition, it can suppress both monocomponent and multicomponent interferences. The simulations show that the proposed method outperforms time-frequency (TF) methods, that successfully deal with multicomponent interferences, in terms of the error probability and computational complexity. 相似文献
99.
The linear relationship between Doppler centroid and range walking in spaceborne SAR data is analyzed, and a new method to estimate Doppler centroid is proposed, which is so called amplitude correlation method. Compared with clutter-lock method which is widely used now, the new method has much less computation burden and is able to give higher estimation accuracy for a quasi-homogeneous scene or a non-homogeneous scene. This is clearly verified by the experimental results of estimating Doppler centroid for SEASAT-A raw data. 相似文献
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