共查询到17条相似文献,搜索用时 171 毫秒
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在合成孔径声纳成像优化的研究中,传统距离-多普勒算法主要应用于窄带窄波束信号合成孔径成像,而在合成孔径声纳领域,由于信号带宽较大,波束较宽,使得成像效果较差.研究了经典距离-多普勒算法的原理,提出了其局限性,针对合成孔径声纳的宽带宽波束信号特点改进了传统算法.放弃窄带信号条件下的Fresnel近似,利用更精确的适用于宽带宽波束信号的距离双曲线模型对算法进行了推导,并在推导结果的基础上对成像区域中任意点目标上进了仿真.仿真结果表明,改进算法具有更高的分辨率和适中的运算量,比传统距离-多普勒算法更适合应用在合成孔径声纳成像中. 相似文献
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针对多接收子阵合成孔径声呐(SAS)精确二维谱表达式复杂,从而只能应用于RD算法的问题,提出将严格解析谱的距离徙动近似为斜距变量的线性函数,然后利用Chirp-z变换校正距离徙动,并给出基于严格解析谱的多接收子阵SAS CZT算法.提出的基于严格解析谱的算法避免了插值操作,提高了算法效率与相位保真度,仿真实验表明,提出... 相似文献
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合成孔径声纳(SAS)中由于基阵相对目标的运动导致回波空间产生了距离徙动,距离徙动的出现将会较大地影响最终声纳的成像质量,目前主要采用插值的方法进行矫正。该文基于SAS中的距离一多普勒(R—D)算法,讨论了距离徙动的成因及矫正思想,详细介绍了几种用于徙动矫正的经典插值方法,并给出了其在SAS成像中的应用表达式,对其性能进行了比较。最后对点目标进行了仿真成像,给出了矫正前后的目标图像,并对不同插值方法的成像质量及运算量进行了分析比较。分析结果表明,这几种插值方法都改善了成像的质量,但拉格朗日法和香农法在改善图像方位向性能上更有优势,可在实际中应用。 相似文献
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传统的相位梯度自聚焦(PGA,phase gradient autofocus)算法仅适用于窄带聚束式合成孔径成像。提出了一种适用于宽带条带式合成孔径声纳的相位梯度自聚焦(SPGA,stripmap phase gradient autofocus)算法。SPGA算法通过多普勒频移估计线性侧摆;SPGA算法消除了侧摆对回波信号包络的影响,使成像模糊仅仅是由方位向相位误差引起的,这样才可以由Dechirp后的距离压缩域数据的相位误差梯度得到侧摆的估计;SPGA算法利用估计得到的侧摆对距离徙动校正前的回波数据进行包络和相位补偿。仿真表明该算法有效地估计出了侧摆,提高了成像质量,且成像没有发生方位向偏移,明确地确定出了目标的位置。 相似文献
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针对强干扰严重影响线列阵声纳弱目标检测的问题,融合盲源分离(Blind source separation,BSS)与波束形成提出了一种抑制方向性强干扰的方法.首先在干扰方位形成波束得到干扰信号估计,然后对阵列接收信号的每个子带采用盲源分离方法得到分离信号和解混矩阵估计,并通过对分离信号和干扰信号进行子带谱相关抑制干扰,再将抑制干扰后的分离信号重构回阵元域信号,最后采用波束形成方法完成目标方位估计.利用模拟器数据和海试数据对方法进行了验证,结果表明,该方法能有效地抑制方向性强干扰,明显提高了弱目标信号的空间谱能量,增强了声纳检测弱目标的能力. 相似文献
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In this article, a novel Scan mode synthetic aperture radar (SAR) imaging method for maritime surveillance is presented. Conventional Scan SAR is generally operated with severe azimuth resolution loss in order to cover a large area. The proposed imaging method changes the way Scan SAR illuminates sub-scenes and presents a new radar illuminating strategy based on ships’ spatial distribution in each sub-scene. To gain ships’ spatial distribution, a scene sensing algorithm based on radar range profiles together with a peak-seeking and clustering algorithm is introduced. After that, a Markov transfer-probability matrix is generated to make sure that radar illuminates each sub-scene randomly under the probability we calculated before. Finally, an imaging algorithm within the Lp (0 < p ≤ 1) regularization framework is utilized to reconstruct each sub-scene; the regularization problem is solved by an improved iterative thresholding algorithm. The whole wide swath image is joined by putting all the sub-scenes together. Experimental results support that the proposed imaging method can perform high-resolution wide swath SAR imaging effectively and efficiently without reducing the image resolution. 相似文献
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利用海洋宽幅SAR图像进行大范围海域舰船检测在海洋监视、军事侦察等方面具有重要应用。由于海况的复杂性,宽幅SAR图像背景杂波特性随海域不同而变化。采用双参数CFAR检测算法和基于K分布CFAR检测算法在处理宽幅SAR图像时,由于在待检测的所有区域采用同种背景杂波模型,导致使用的杂波模型在不适应区域失配,使CFAR检测性能下降。针对这个问题,提出了一种基于自适应背景杂波模型的CFAR宽幅SAR图像舰船检测算法,该算法通过背景窗口的多尺度统计方差判断目标所处的杂波环境,自适应选择对应的背景杂波分布模型,最后根据已知的恒虚警率及选择的杂波概率密度函数进行CFAR检测。对20多幅宽幅SAR图像进行了试验,实验结果表明:该算法在检测精度上有明显的改善。 相似文献
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Roll angle is an important parameter for three-dimensional imaging altimeter to measure Sea Surface Height.The height error due to the roll angle error grows linearly across the swath and a slight error of roll angle will results in a large height error within observation range.So a very accurate knowledge of the roll angle error is required.Nadir interferometric phase has a strong correlation with the roll angle,so using the nadir interferometric phase from the interference image can get roll angle more accurately than instrument measurements.It’s possible to meet the centimeter-level accuracy after correcting the roll angle error.Simulation measurement and elevation reconstruction based on the geometric relationship were performed,and the research of correction the roll angle error by nadir interferometric phase was carried out.Both theoretical calculation and numerical simulation show that the measurement accuracy of roll angle can be as high as 0.03 arcsecond when the accuracy of nadir interferometric phase is 10-3rad.In this case,the height measurement accuracy have been averaged across a swath between 10 and 60 km of nadir will decrease to 0.48 cm which is 6.02 cm when the roll accuracy is 0.36 arcsecond.It means that the nadir interferometric phase method can effectively correct the roll error of three-dimensional imaging altimeter. 相似文献
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Iterative learning control (ILC) for a galvanometer scanner is proposed to achieve high speed, linear, and accurate bidirectional scanning for scanning laser microscopy. A galvanometer scanner, as a low stiffness actuator, is first stabilized with a feedback control compensating for disturbances and nonlinearities at low frequencies, and ILC is applied for the control of the fast scanning motion. For stable inversion of the non-minimum phase zeros, a time delay approximation and a zero phase approximation are used for design of ILC, and their attainable bandwidths are analyzed. Experimental results verify the benefits of ILC of its wide control bandwidth, enabling a faster, more linear, and more accurate scanning without a phase lag and a gain mismatch. At the scan rate of 4112 lines per second, the root mean square (RMS) error of the ILC can be reduced by a factor of 73 in comparison with the feedback controlled galvanometer scanner of the commercial system. 相似文献
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R. K. RANEY 《International journal of remote sensing》2013,34(5):991-998
Abstract A new imaging algorithm is presented for Synthetic Aperture Radar (SAR) that is exact in the sense that it is capable of producing a complex image with excellent geometrical, radiometrical and phase fidelity. No interpolations or significant approximations are required, yet the method accomplishes range curvature correction over the complete range swath. The key to the approach is a quadratic phase perturbation of the range linearly frequency modulated signals while in the range signal, azimuth frequency transform (Doppler) domain. Range curvature correction is completed by a phase multiply in the two-dimensional frequency domain. Other operations required are relatively conventional. The method is generalizable to imaging geometries encountered in squint and spotlight SAR, inverse SAR, seismics, sonar, and tomography. 相似文献
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The problem of calibration has arisen because the phase characteristics of signal paths associated with each antenna in a smart antenna system (SAS) are different (in both receiving (RX) and transmitting (TX) modes). In this paper, we propose a simple and accurate calibration technique for eliminating the phase characteristic difference of the signal path associated with each antenna element in both RX and TX modes. Also, through the experimental data obtained from SAS, which has been implemented with the CDMA2000 1X standard, we confirm that the proposed technique has eliminated the characteristic difference. 相似文献