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双基地声纳系统中存在目标信号与直达波干扰混叠且两者高相关的情况,常规的自适应抵消法因此失效。在双基地声纳系统配置已知的前提下,提出一种基于零陷展宽技术的多约束最小方差直达波抑制算法。该方法通过施加线性约束对特定方向的干扰进行抑制,并针对直达波干扰方位存在扰动时,多约束最小方差算法性能急剧下降的现象运用零陷展宽的方法对算法加以改进。基于零陷展宽的多约束最小方差算法直观、快捷。仿真及实验数据处理的结果表明,在直达波干扰方位大致可知的情况下,该算法能够对直达波进行有效抑制,且对直达波的方位估计误差具有稳健性。 相似文献
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针对舰艇编队作战中主动声纳之间存在的强直达波干扰,提出了一种基于信号统计二阶矩的直达波干扰抑制算法,实现了强干扰背景下的微弱目标回波检测。这种方法将盲分离理论和匹配相关技术相结合,首先对接收数据进行直达波干扰抑制,再利用已知发射信号副本进行匹配相关,最后提取目标回波信号。相比其它强干扰抑制算法,特别是高阶累计量法,该算法具有计算复杂度低的优点。通过数值仿真实验表明:该算法能够对直达波干扰进行有效抑制,对目标回波的检测性能优于直接匹配相关方法。 相似文献
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为了克服主动声呐编队作战条件下的直达波干扰,达到检测微弱目标回波信号的目的.提出了一种基于频域分块自适应滤波算法的直达波抑制方法。这种方法将自适应滤波理论和匹配相关技术相结合,首先对接收数据做频域分块自适应滤波,再利用已知发射信号副本进行匹配相关,最后提取目标回波信号。其中,频域分块自适应滤波算法相比基本最小均方算法,计算复杂度降低,收敛速度快,基本保证了主动声呐每个探测周期内的直达波抑制和目标回波的提取。通过数值仿真实验表明:在强直达波干扰存在条件下,该算法对目标回波的提取在精度和鲁棒性等方面均优于以往的直接匹配相关方法。 相似文献
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本文根据散射矩阵方法模拟等离子体并建立了非均匀等离子体理论模型,并在此基础上计算了0.1 THz^10 THz频段的全波段太赫兹波在其中的传输特性。根据介质阻挡放电原理在实验室环境下搭建等离子体射流产生装置并产生非均匀等离子体,进行了太赫兹时域光谱(THz-TDS)以及宽带太赫兹源在等离子体中的透射光谱测量以及太赫兹波对等离子体遮挡下目标物的反射成像的试验。理论和实验结果均表明,较高频太赫兹波在等离子体中有良好的穿透性,这为太赫兹波在黑障区的通信以及雷达探测应用打下研究基础。 相似文献
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基于粒子模拟技术研究了螺旋线行波管的时域非线性理论,慢波结构中的场通过螺旋带模型求解得到,并考虑了夹持杆和屏蔽桶的影响,推导得到了注-波互作用的动理学方程;聚焦磁场可以是直流磁场也可以是周期永磁场;用泊松方程求解得到空间电荷场;注-波互作用方程用MacCormack的差分格式进行计算。给出了时域计算得到的瞬态特性,并与基于一维Christine及三维Christine理论的计算结果进行了比较。 相似文献
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为了去除直达波干扰,从强的直达波干扰背景中有效提取SISAR侧影成像的目标全息信号,提出了对接收的含有目标全息信号和强直达波的混合信号直接进行包络检波,然后通过对检波后的输出进行时域的正交分解,恢复目标的全息信号的新方法.仿真结果验证了理论分析的正确性。 相似文献
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Non-line-of-sight identification in ultra-wideband systems based on received signal statistics 总被引:1,自引:0,他引:1
Non-line-of-sight (NLOS) propagation can severely degrade the reliability of communication and localisation accuracy in indoor ultra-wideband (UWB) 'location-aware' networks. Link adaptation and NLOS bias mitigation techniques have respectively been proposed to alleviate these effects, but implicitly rely on the ability to accurately distinguish between LOS and NLOS propagation scenarios. A statistical NLOS identification technique based on the hypothesis-testing of received signal parameters in UWB propagation channels is discussed. In contrast to narrowband and wideband signals, UWB signals possess higher temporal resolution and robustness to multipath fading. We show that these characteristics result in differences in the statistics of (a) the time-of-arrival (TOA), (b) the received signal strength (RSS) and (c) the root-mean-squared delay spread (RDS) of the received signals, between LOS and NLOS propagation scenarios, which can be exploited for accurate channel identification. We statistically characterise the ability of TOA, RSS and RDS estimates to distinguish between LOS and NLOS propagation based on an extensive indoor measurement campaign. Our measurement results suggest that the RDS of UWB signals can, even in isolation and without complete statistical information, serve as a robust and computationally efficient indicator of the LOS/NLOS nature of propagation. Finally, we demonstrate the efficacy of the discussed NLOS identification method in a location- tracking application based on indoor UWB measurements. 相似文献
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This study presents sample measurements and analysis characterising the radio channel for outdoor short-range sensor networks. A number of transmit and receive antennas are placed on the ground in an open area. The measured propagation channel is time varying because of the controlled motion of a person walking in the vicinity of the nodes. The statistics of both the line-of-sight (LOS) path and the scattered component of the measured channel are observed to be non-stationary. The channel (power) gains are found to be significantly influenced by the pedestrian movement, only when the LOS path is momentarily blocked. The authors present a generic approach to model receive signal fluctuations because of body blockage of the LOS path. Our approach, which is similar to the referenced work of Pagani and Pajusco, additionally models the time-variant Doppler spectrum of the residue (scattered) component of the measured channel, that is the remainder of the measured channel after the LOS path has been extracted. The proposed modelling approach is parameterised and validated from the measurements. 相似文献
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Wei Zhang 《Journal of research of the National Institute of Standards and Technology》1999,104(6):579-584
This paper presents a closed-form expression for multiple forward diffraction by rows of tree canopies and buildings applicable to the propagation predictions at centimeter and millimeter wavelengths for local multipoint distribution service (LMDS). The expression is derived from the uniform geometrical theory of diffraction and physical optics, as well as from some existing models for vegetation and buildings. When the transmitter antennas are sufficiently high, the attenuation of the buildings varies around the value of free space and the building effect is negligible, because a line-of-sight (LOS) propagation path between transmitter and over building-rooftop receiver antennas exists and plays a major role. The tree canopies which extend above the building rooftop heights block the LOS propagation path and cause additional signal attenuation. An existing study of the LMDS radio channel based on measurements came to the same conclusion. The attenuation effect of the buildings is significant if the transmitter antennas are not high enough. 相似文献
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舰载视轴稳定系统的变结构控制研究 总被引:2,自引:0,他引:2
为了消除舰船摇摆对舰载光电跟踪设备稳定精度的影响,提高系统视轴稳定性能,根据舰船摇摆对视轴偏差影响的随机性,在描述视轴稳定回路的基础上,设计视轴稳定滑模变结构控制器,并引入约束条件,以减弱系统抖振.利用AR序列预测估计方法,实现视轴偏差预测估计,完成视轴稳定滑模变结构控制律的求取,并利用matlab仿真软件,对视轴稳定滑模变结构控制律进行数字计算.仿真结果表明,该控制方法能有效地消除了陀螺测量随机噪声带来的影响,减弱了系统抖振,对舰载视轴稳定有良好的性能. 相似文献
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通过相关莱斯信道模型对海面散射水声多入多出(MIMO)信道容量进行了研究。从Helmholtz-Kirchhoff积分和Fresnel近似出发,得到海面散射信号的空间相关性,由于信道的协方差矩阵不可以表示成发射相关矩阵和接收相关矩阵的Kronecker积,通过Monte Carlo仿真研究了莱斯因子、接收信噪比和空间相关性对MIMO信道容量的影响。从对outage capacity和信道容量的CCDF(Complementary Cumulative Distribution Function)的仿真计算结果可以看出,莱斯衰落的MIMO信道容量并不总是小于瑞利衰落MIMO信道容量,当信道的空间相关性较大和接收信噪比较小时,由于信道的衰落作用将起主要作用,对于较小的收发阵元数,以非衰落的直达信号为主的莱斯MIMO信道容量将大于瑞利衰落的MIMO信道容量。 相似文献
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混合噪声背景下正弦参数估计的互高阶谱Pisarenko方法 总被引:6,自引:1,他引:5
本以互四阶累积量为依据,首次证明了互高阶累积量可以有效地抑制非相关噪声和高斯噪声;并在建立互高阶累积量的Yule-Walker方程的基础上,通过该矩阵的奇异值分解,建立了信号矢量空间与噪声矢量空间;首次提出了混合噪声背景下正弦参数估计的互高阶谱Pisarenko方法。仿真结果表明,与自高阶谱Pisarenko方法相比,该方法具有更好的谱估计的分辨率和谱估计的稳定性,抗干扰性更强,其信噪比工作门限更低,特别适合于工程中小信号的测量。 相似文献
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电子细分是光栅位移传感器实现纳米级分辨率测量的关键,细分误差由细分方法和光栅信号质量共同决定。针对信号实时修正方法在小步距测量和一些复杂工况环境下的局限性,从提高细分方法对非理想光栅信号的适应性的角度出发,提出了基于信号比值线性化的新型电子细分方法,构建了2种实时补偿信号以进一步提高信号的线性度;详细阐述了所提细分方法的细分原理,分析了其在非理想光栅信号输入情况下的细分误差;实现了最高为0.003μm的理论细分精度和0.08μm的实际细分精度。数值仿真和对比实验结果表明,所提细分方法对非理想光栅信号的适应性明显优于常用的反正切细分法和正余弦绝对值相减细分法。 相似文献
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针对滚动轴承微弱故障信号难以检测的难题,提出一种基于新型非线性耦合双稳态随机共振模型的轴承微弱故障信号增强检测方法。噪声背景下,随机共振可以实现微弱信号的增强输出,提高微弱信号特征的检测。提出的非线性耦合双稳态系统是由两个单一双稳态系统经非线性方式耦合而成,通过分析耦合系数、阻尼系数随着噪声强度改变的信噪改善比响应特性曲线图研究了不同参数对随机共振现象的影响。结果表明,耦合双稳系统比单一双稳态系统具有更强随机共振现象的产生。最后采用模型对轴承故障微弱信号进行了增强检测应用,所提出的非线性耦合双稳态随机共振能够实现在复杂的噪声背景下对微弱故障信号的检测。 相似文献