共查询到19条相似文献,搜索用时 265 毫秒
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海洋环境的复杂性和多变性严重影响了水下信号处理系统的性能。若能在信号处理之前辨识出海洋环境参数,并将其融入信号处理框架中,则有希望提高信号处理器的性能,得到更好的滤波、检测、定位和跟踪效果。将海洋环境建模为高斯-马尔可夫模型,利用声速梯度数据和由Kraken模型得到的声压场数据,结合扩展的卡尔曼滤波器算法,实现了对简正波的估计。利用该模基处理方法,可以辨识出简正波的模函数和水平波数,并能估计出基阵所在位置的声压场。在两种典型浅海声场环境下进行的计算机仿真证明了算法的有效性。 相似文献
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浅海环境中,目标回波受到入射和散射双向过程的信道多途影响,具有复杂的多途结构。基于相控垂直阵的单模发射技术能激发出指定的单个简正波声场,可以降低海底混响干扰,简化目标回波多途结构,为主动探测提供了一种有效手段。在信道中点声源目标回波模型基础上,采用简正波本征函数加权研究了单模声场入射下球形目标散射问题,建立了浅海单模入射声场目标回波预报模型,并利用模型对刚性球回波进行了数值计算。结果表明:总声源级相同条件下,单模发射声场与传统的点声源发射声场相比具有一定的阵发射增益,目标回波具有较高的声压级;单模入射能够消除单程多途的影响,回波结构相对简单,有利于目标的探测和识别。 相似文献
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为提高宽带简正波本征值的计算效率,汉密尔顿方法通过公式变换抵消频率项,将宽带简正波本征值的计算由频率、本征值实部和虚部的三维寻根降低至本征值实部和虚部的二维寻根,可以一次性求解单号简正波所有频率对应的简正波本征值。在已有工作的基础上优化和完善了汉密尔顿宽带简正波本征值算法,并加入并行计算方法进一步提高计算效率。以简正波模型KRAKENC作为对比,通过若干数值算例验证了该算法对于宽带简正波本征值的计算精度和计算效率。数值仿真结果显示,在保证宽带简正波本征值计算精度的前提下,该方法的计算效率相对KRAKENC有着明显的优势;加入并行算法后,该方法的计算效率得到大幅提高。 相似文献
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在多波束测深声呐的工作环境中,若海底反向散射信号不满足点源假设,方位估计精度将严重下降,而基于分布源模型的方位估计算法可以适应这种环境。目前,大多数分布源算法要求分布源之间不相干,有人提出采用Toeplitz方法估计相干分布源,但该方法精度不高并且忽略了角度扩展参数。为解决多波束测深声呐相干分布源的方位估计问题,提出了基于空间平滑的广义MUSIC方法,公式推导证明了算法的有效性,通过计算机仿真给出算法方位估计的精度以及不同信噪比条件下的性能,最后采用多波束测深系统的实验数据对算法进行了验证。 相似文献
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提出了在Pekeris波导条件下,一种基于波数积分方法的线源声场中的稳定数值计算方法。通过对深度格林函数中上行波与下行波的归一化,得到稳定的系数矩阵,从而求得格林函数的解析解。对深度格林函数进行模式展开,验证了该方法得到的深度格林函数解析解的准确性。结合仿真实例,将该方法得到的波数积分模型与传统简正波模型KRAKENC的结果进行比较,结果显示,当某号简正波的波数与海底波数接近时,KRAKENC计算不出该号简正波,会导致KARKENC的计算结果不准确,而波数积分方法可以很好地解决该问题。因此,提出的方法可以作为Pekeris波导中线源激发声场的标准模型。 相似文献
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物理学家莫尔斯提出的室内受迫振动简正波理论在数学处理上无懈可击,但是,其声压解全部由简正波组成,无法直接观察到直达声的存在,因此,近些年来受到国内一些学者的置疑:该简正波理论解是包括直达声的全部解,还是不包括直达声的部分解?本文在傅立叶分析和狄拉克函数的基础上,经过严格的数学推导,证明莫尔斯简正波理论关于室内声源的基本假设是正确的,其物理涵义是:室内任意一个声源分布及由室内壁面反射引起的一系列镜像声源组合后可表示为分立简正函数的迭加,回答了国内一些学者对莫尔斯的室内声源基本假设的置疑。此外,在空间域上由简正波解推导出了射线解,证明室内受迫振动简正波理论与镜像原理完全等价。据此,认为简正波理论解是室内稳态声场的完备解。 相似文献
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This study estimates the time of arrival (TOA) of ultra wideband multipath components (MPCs) by analysing the spatial correlation of multipath signals captured by a 7times7 antenna array. In this study, both line-of-sight and non-line-of-sight radio propagation paths were considered. Each power-delay profile bin from all the array positions was used to calculate the spatial correlation between itself and the adjacent receiving point bins. Consequently, some MPC time delays and clusters, associated with high correlation values, were selected and compared with the TOA computed by the Sensor-CLEAN algorithm. A close agreement of the TOA estimated by both techniques was obtained. Finally, multipath cluster distributions and clustering model parameters are presented and compared with previously published results 相似文献
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Abstract In mobile communication systems, local scatterers in the vicinity of the sources cause angular spreading of radiating signals as seen from a base station antenna array. Thus, the base station antenna array is typically situated on the roof of a high building away from potential multipath reflectors. The uniform circular array (UCA) geometry provides 360° azimuthal coverage and also provides information on source elevation angles. We consider the problem of two‐dimensional (azimuth and elevation) direction‐of‐arrival (DOA) estimation with UCA. In the multipath scenario, the base station antenna can receive many coherent signals that cause the array manifold to be different from the conventional array manifold model. Herein, parameters of the spatial signature in the presence of local scattering are presented which apply to UCA. Then, we present a fast searching technique to improve the efficiency of the MUSIC algorithm for two‐dimensional DOA estimation. The fast signal subspace‐based estimation method utilizes the ESPRIT algorithm and then adopts sequential one‐dimensional searching to save computational cost. Several simulation results are included for illustration and comparison. 相似文献
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Space-time constant modulus algorithm for multipath removal on the reference signal exploited by passive bistatic radar 总被引:1,自引:0,他引:1
Colone F. Cardinali R. Lombardo P. Crognale O. Cosmi A. Lauri A. Bucciarelli T. 《Radar, Sonar & Navigation, IET》2009,3(3):253-264
The authors address the problem of multipath cancellation in the reference signal used in passive bistatic radar (PBR), which exploits an existing transmitter as emitter of opportunity. The presence of multipath echoes in the reference signal is demonstrated to strongly affect the detection performance of passive radar. Based on the well-known constant modulus algorithm (CMA) approach in the time-domain, new multi-dimensional techniques are considered for the adaptive equalisation of the reference signal based on an array of antennas and multiple receiving channels. The effectiveness of these techniques for PBR purposes is demonstrated with reference to typical simulated scenarios. The considered strategies, addressed as space-CMA and space-time-CMA, are shown to be able to recover the performance loss because of the multipath contribution in the reference signal so that they appear as very appealing solutions for PBR equipped with an array of antennas and multiple receiving channels. 相似文献
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使用训练序列构成的测量矩阵并采用稀疏恢复算法是近年来常用的多径稀疏信道估计思路。提出一种贝叶斯匹配追踪算法的正交化改进方法,有效地改善了原方法的收敛速度,并将其应用于水下多径稀疏信道估计。进行了新方法的理论推导和两种水下稀疏信道模型中的仿真试验,进而与传统贪婪迭代和贝叶斯估计方法的估计效果进行了对比。仿真结果证明,所提出的新方法比原方法的收敛速度更快,能更高效地进行多径稀疏信道估计。新方法在低信噪比和呈簇状集中分布的水下多径稀疏信道中也有更好的估计效果。 相似文献
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水平阵是水声通信中常见的阵列接收形式,但垂直阵也有重要的应用场合。文章提出了一种适用于垂直阵的水声通信多通道最大似然联合均衡译码方法,相比现有仅在信道均衡中叠加各通道信号的多通道判决反馈均衡方法(Multichannel Decision Feedback Equalizer, M-DFE),该方法利用最大似然准则,在一体化联合均衡译码过程中融合空间多通道接收信息,将空间增益直接用于抵抗水声信道多途衰落和译码纠错,有效提升了水声通信的性能。仿真结果表明,在误码率同样达到 10-3的条件下,该方法所需信噪比相比 M-DFE方法可下降 2 dB。海上实验结果显示,在多种信道条件下,该方法实现正确译码的通信速率是 M-DFE方法的 1.25倍以上。 相似文献
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McGough RJ Cindric D Samulski TV 《IEEE transactions on ultrasonics, ferroelectrics, and frequency control》2001,48(2):494-505
A conformal ultrasound phased array prototype with 96 elements was previously calibrated for electronic steering and focusing in a water tank. The procedure for calibrating the shape of this 2D therapy array consists of two steps. First, a least squares triangulation algorithm determines the element coordinates from a 21×21 grid of time delays. The triangulation algorithm also requires temperature measurements to compensate for variations in the speed of sound. Second, a Rayleigh-Sommerfeld formulation of the acoustic radiation integral is aligned to a second grid of measured pressure amplitudes in a least squares sense. This shape calibration procedure, which is applicable to a wide variety of ultrasound phased arrays, was tested on a square array panel consisting of 7-×7-mm elements operating at 617 kHz. The simulated fields generated by an array of 96 equivalent elements are consistent with the measured data, even in the fine structure away from the primary focus and sidelobes. These two calibration steps are sufficient for the simulation model to predict successfully the pressure field generated by this conformal ultrasound phased array prototype 相似文献