共查询到18条相似文献,搜索用时 156 毫秒
1.
2.
3.
4.
建立一种复杂结构水听器基阵阵列流形计算模型。该模型运用声场计算的边界元方法,通过计算任意散射体表面声场分布,求出基阵阵元位置处声场响应,进而得到基阵阵列流形;基于该阵列流形,运用波束设计方法求出阵元权值,分别利用实测和理论阵列流形得到基阵实测波束以及理论波束。针对安装在半球形硬质铝壳体上的圆弧阵进行的水池实验,实验结果表明实测阵列流形和基于边界元方法的计算结果基本吻合,实测波束和理论波束相差不大,并且性能均优于按无指向性点接收器经相位补偿后相加所得到的波束。 相似文献
5.
在信号频率一定的情况下,常规波束形成方法需要通过增大基阵孔径来提高目标方位的估计精度,但这会受到实际工程应用的限制。在研究矢量水听器波束形成的基础上,提出了基于Taylor级数展开的虚拟阵元波束形成方法。该方法针对有限尺度双十字阵型的矢量水听器基阵,根据已知阵元接收的数据,运用Taylor级数展开方法估计虚拟阵元上的接收数据,使基阵孔径在虚拟意义上得以扩大。从而改善了阵列的波束性能,窄化主瓣和抑制旁瓣,实现了空间分辨率的提高。仿真和试验数据结果证明了该方法的有效性。 相似文献
6.
7.
为了不增大阵列尺度采用信号处理方法得到高分辨率的波束指向性,首先利用Notch滤波器的"离线重构"实现窄带波束形成,进而结合其瞬时相位估计方法,研究了基于自适应Notch滤波器的恒定束宽波束形成技术,利用信号处理方法将矢量传感器阵列接收的低频窄带信号转化为具有指向性的较高频率波束,并采用虚拟阵元技术消除波束栅瓣的影响,给出了实际应用中具体的信号处理方法。仿真和湖试验证表明这种基于自适应Notch滤波器的恒定束宽波束形成方法是合理可行的。最后,针对适应实时信号处理的要求提出将这种方法与目标自动跟踪系统相结合的改进方向。 相似文献
8.
基于心形指向性传声器的波束形成可以有效抑制阵列后方声源的干扰,提高前方声源的识别精度。以平面轮形传声器阵列为对象,借助MATLAB仿真计算,对阵列后方声源波束形成声源识别特性及其抑制方法进行研究。基于除自谱的互谱波束形成算法提出了含有传声器指向性的波束形成算法,对圆形和心形指向性传声器进行不同声源类型的波束形成仿真计算,并针对仿真结果显示出的不足,给出了既能保证阵列平面上最大声压贡献量的识别精度,又能降低旁瓣水平的幅值校正算法。试验结果证明了基于心形指向性传声器的波束形成可以有效抑制后方声源。 相似文献
9.
高分辨波束形成器比常规波束形成具有更好的方位分辨力与干扰抑制能力。该波束形成器能够提高阵列输出信干噪比,从而提高声呐的探测性能。与多重信号分类、旋转不变子空间等方法相比,最小方差无畸变响应(Minimum Variance Distortionless Response,MVDR)波束形成器输出真实反映了观察方向的信号功率,同时可提供波束时间序列做后置处理,在水声阵列处理领域得到了快速发展和深入研究。对高分辨MVDR技术在水声阵列处理中的研究进展进行了回顾,重点介绍了其宽带处理、稳健性、运动补偿、解相干等国内外的研究热点和最新成果,同时给出其在各种水声阵列处理领域的应用前景。 相似文献
10.
11.
12.
13.
14.
15.
Decoupled Beamforming and Noise Cancellation 总被引:1,自引:0,他引:1
《IEEE transactions on instrumentation and measurement》2007,56(1):80-88
The enhancement of noise-corrupted speech acquired by microphones is indispensable to the functioning of a wide variety of digital signal processing algorithms. Many existing products are equipped with steerable, stand-alone fixed beamformers which provide moderate levels of directivity. Moreover, many applications have long employed the classical adaptive noise canceller configuration with a reference sensor near the noise source to cancel unwanted noise. In this paper, the cascading of stand-alone beamformers with back-end adaptive noise cancellers is studied. A decoupled model for signal enhancement using front-end beamformers and cascaded noise cancellers is presented. The inter-operation of the beamforming and noise canceling units is studied by defining the signal-to-interference ratio (SIR) gain, directivity index, and white noise gain offered by the beamforming and noise cancelling components. The performance of decoupled beamformer-noise canceller structures is evaluated using experimental measurements. An experimental procedure for evaluating output SIR is presented. Results reveal SIR improvements of up to 27 dB, and are compared to those stemming from conventional adaptive beamformers 相似文献
16.
Hydrophone spatial averaging corrections from 1 to 40 MHz 总被引:2,自引:0,他引:2
Radulescu E.G. Lewin P.A. Goldstein A. Nowicki A. 《IEEE transactions on ultrasonics, ferroelectrics, and frequency control》2001,48(6):1575-1580
The purpose of this study was to develop and experimentally verify a practical spatial averaging model for frequencies up to 40 MHz. The model is applicable to focused sources of circular geometry, accounts for the effects of hydrophone probe finite aperture, and allows calibration by substitution to be performed when the active elements of reference and tested hydrophone probes differ significantly. Several broadband sources with focal numbers between 3 and 20 were used to produce ultrasound fields with frequencies up to 40 MHz. The effective diameters of the ultrasonic hydrophone probes calibrated in the focal plane of the sources ranged from 150 to 500 μm. Prior to application of the spatial averaging corrections, the hydrophones with diameters smaller than that of the reference hydrophone exhibited experimentally determined absolute sensitivities higher than the true ones. This discrepancy increased with decreasing focal numbers and increasing frequency. It was determined that the error was governed by the cross-section of the beam in the focal plane and the ratio of the effective diameters of the reference and tested hydrophone probes. In addition, the error was found to be reliant on the frequency-dependent effective hydrophone radius. After applying the spatial averaging correction, the overall uncertainty in the hydrophone calibration was on the order of ±1 dB. The model developed is being extended to be applicable to frequencies beyond 40 MHz, which are becoming increasingly important in diagnostic ultrasound imaging applications 相似文献
17.
摘要:在对水下目标进行探测识别的应用中,一般要求声纳系统具备在较宽频带内形成恒定束宽波束的能力:过去对声纳恒定束宽波束形成器的研究一直针对声压水听器阵,近来随着对矢量水听器认识的深入,开展基于矢量水听器阵的恒定束宽波束形成器研究越发变得必要。本文正是体现了作者在这一方面的阶段性研究成果。文中首先介绍了单个矢量水听器的指向特性,接着提出了矢量水听器阵宽带恒定束宽波束形成器的实现原理和设汁方法,并以均匀等间距线阵为例,给出了获得实现恒定束宽算法所需频域加权矩阵的步骤,之后又进一步给出了恒定束宽算法的频域实现流程,并通过计算机仿真验证了其有效性: 相似文献
18.
Harris GR 《IEEE transactions on ultrasonics, ferroelectrics, and frequency control》1991,38(5):413-417
To examine how less-than-ideal hydrophones and amplifiers could affect the measurement of pulse parameters, a simulated distorted pressure pulse is analyzed before and after being filtered by hydrophone and amplifier response models. The hydrophone model used is similar to the response of piezopolymer membrane hydrophones. The amplifier model is taken from typical responses of integrated circuit operational amplifier-based designs. The pressure pulse, hydrophone, and amplifier are characterized respectively by the pulse center frequency, f (c), the hydrophone resonance frequency, f(h), and the amplifier low-pass corner frequency, f(a). 相似文献