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1.
Migration through resolution cell compensation in ISAR imaging 总被引:5,自引:0,他引:5
Mengdao Xing Renbiao Wu Jinqiao Lan Zheng Bao 《Geoscience and Remote Sensing Letters, IEEE》2004,1(2):141-144
Range-Doppler (RD) processing is widely used in conventional inverse synthetic aperture radar (ISAR) imaging. The unwanted translational motion of moving targets is compensated by envelope alignment and autofocus. For existing ISAR imaging algorithms, the scatterers' migration through resolution cells (MTRC) caused by the rotational motion is usually ignored. With the improvement of resolution or the increase of target size, MTRC cannot be neglected. In this letter, the keystone formatting algorithm developed in SAR is used for the MTRC compensation in ISAR. Before the keystone formatting, coherent processing must be performed on the raw phase history data. An effective approach is proposed for this kind of coherent processing. Numerical examples are provided to demonstrate the performance of the proposed approach. 相似文献
2.
Liping Du Guangchuan Su 《Geoscience and Remote Sensing Letters, IEEE》2005,2(3):247-249
A novel adaptive inverse synthetic aperture radar (ISAR) imaging technique is proposed for targets with nonuniform motion. The proposed algorithm is referred to as the generalized range-Doppler (GRD) ISAR imaging technique and is based on the fractional Fourier transform (FRFT). By utilizing this technique, clear ISAR imaging can be achieved for nonuniformly moving targets without involvement of complex motion compensation. Simulation results have proved that the new algorithm is robust and also computationally efficient as compared with previously reported algorithms such as joint time-frequency (JTF) imaging. 相似文献
3.
Changzheng Ma Tat Soon Yeo Hwee Siang Tan Jun Wang Baixiao Chen 《Geoscience and Remote Sensing Letters, IEEE》2008,5(3):378-382
4.
加速迭代硬阈值(AIHT)作为一种压缩感知(CS)算法,具有计算复杂度低、内存占用小的特点,在较小数目的观测下,经过有限次迭代便能获得较好的重建效果。因此,本文将该算法应用到逆合成孔径雷达(ISAR)稀疏成像,对该方法的具体特征和适用性进行了详细分析。仿真结果表明,在相同信噪比和回波脉冲数条件下,基于AIHT的ISAR成像方法,相比于稀疏贝叶斯算法(SBL),在重建时间上缩短了至少2个量级;相比于迭代加权最小二乘法(IRLS)和平滑l0范数算法,在重建质量上提高了约3倍。经实测数据处理结果验证,在1/4原始脉冲数条件下,该方法仍具有良好的聚焦性能和压低旁瓣效果。 相似文献
5.
Xiaowei Hu Ningning Tong Xingyu He Yuchen Wang 《Journal of the Indian Society of Remote Sensing》2018,46(3):387-393
In inverse synthetic aperture radar (ISAR) imaging, the image resolution is always limited by the bandwidth and the observation time. Sparse recovery (SR) is recently proposed to improve the range resolution or cross-range resolution effectively. However, for the two dimensional superresolution case, a SR-induced range cell migration (RCM) occurs among the High-Resolution Range Profiles (HRRPs) and definitely degrades the ISAR image. After that translational motion compensation is completed, the common sparsity of HRRPs is exploited to suppress the RCM in this paper. Furthermore, by taking the temporal correlation of HRRPs into account, an ISAR imaging method based on temporally correlated Multiple Sparse Bayesian Learning is proposed to improve the imaging quality. Simulated data and real data results demonstrate the effectiveness of the proposed method. 相似文献
6.
Modified range-Doppler processing for FM-CW synthetic aperture radar 总被引:12,自引:0,他引:12
The combination of compact frequency-modulated continuous-wave (FM-CW) technology and high-resolution synthetic aperture radar (SAR) processing techniques should pave the way for the development of a lightweight, cost-effective, high-resolution, airborne imaging radar. Regarding FM-CW SAR signal processing, the motion during the transmission of a sweep and the reception of the corresponding echo were expected to be one of the major problems. In FM-CW SAR, the so-called stop-and-go approximation is no longer valid due to the relatively long sweeps that FM-CW radars transmit. The main effect of the continuous motion is a Doppler frequency shift throughout the SAR observation time. This Doppler frequency shift can be compensated for by modifying the range migration compensation. 相似文献
7.
The temporal change of the rotation vector of a rotating body is, in the first order, identical in a space-fixed system and
in a body-fixed system. Therefore, if the motion of the rotation axis of the earth relative to a space-fixed system is given
as a function of time, it should be possible to compute its motion relative to an earth-fixed system, and vice versa. This
paper presents such a transformation. Two models of motion of the rotation axis in the space-fixed system are considered:
one consisting only of a regular (i.e., strictly conical) precession and one extended by circular nutation components, which
are superimposed upon the regular precession. The Euler angles describing the orientation of the earth-fixed system with respect
to the space-fixed system are derived by an analytical solution of the kinematical Eulerian differential equations. In the
first case (precession only), this is directly possible, and in the second case (precession and nutation), a solution is achieved
by a perturbation approach, where the result of the first case serves as an approximation and nutation is regarded as a small
perturbation, which is treated in a linearized form. The transformation by means of these Euler angles shows that the rotation
axis performs in the earth-fixed system retrograde conical revolutions with small amplitudes, namely one revolution with a
period of one sidereal day corresponding to precession and one revolution with a period which is slightly smaller or larger
than one sidereal day corresponding to each (prograde or retrograde) circular nutation component. The peculiar feature of
the derivation presented here is the analytical solution of the Eulerian differential equations. 相似文献
8.
为提高对渤海海冰旋转和平移运动的监测精度,提出一种基于投影变换的相位相关跟踪方法。选取连续8景静止水色成像仪(GOCI)图像序列,根据特征图像窗口的投影变换构造辅助函数,通过寻求函数最优解得到旋转角度集合,选择修正相关系数确定最佳旋转角度,同时根据相位信息实现海冰样本间亚像素级别的平移跟踪,消除传统相位相关法中因忽略图像相频特性所造成的匹配误差。实验结果表明,以手动测量的旋转角度为基准,该方法和传统相位相关法的旋转监测均方根误差的最大值/平均值分别为0.59/0.50与1.41/0.94,跟踪速度提高了50.6%;海冰平移运动的速度矢量与辽东湾的现场实测数据及历史资料记录数据基本一致。该方法对渤海海冰旋转和平移运动具有较好的跟踪效果。 相似文献
9.
Yong Wang Yicheng Jiang 《Geoscience and Remote Sensing Letters, IEEE》2009,6(4):658-661
Inverse synthetic aperture radar (ISAR) imaging of a ship target is very important compared with the plane target, and the imaging condition of the ship target is more complicated than that of the plane target due to the complexity of the ship's movement. In this letter, the received signal of a ship target is modeled as a multicomponent cubic phase signal, and the product high-order matched-phase transform is proposed to estimate the parameters of each component. Then, the instantaneous ISAR images can be obtained. Results of real data demonstrate the effectiveness of the new method proposed. 相似文献
10.
传统的机载合成孔径雷达(SAR)一般依赖于GPS/INS组合系统补偿平台的运动误差,并获得高分辨率的图像。GPS获取的地理坐标(即经度,纬度和高度)需要转换为本地的直角坐标,原始雷达数据在这个直角坐标系下才能引入成像及运动补偿算法进行处理,并获得本地直角坐标系下的图像。这种图像是通过局部坐标描述的,对于其他部门是不通用的,因为其他部门需要的是经过全球地理坐标标绘的图像。本文提出了一种由后向投影算法BP(Back Projection)引出的新的SAR成像算法,它直接在地理坐标下处理,可避免坐标转换的过程。而且生成德图像像素均和地理坐标一一对应,能够很方便地被情报或其他部门使用。而且在仿真试验以及外场试验中,证明了本文算法和常规BP算法成像效果是相当的。 相似文献
11.
图像超分辨率重建技术是根据序列图像间信息互补重建高分辨率图像的技术,其主要步骤在于精确运动估计算法和有效超分辨率重建算法。针对存在旋转、缩放变换的序列图像,本文提出一种基于SIFT匹配和随机采样一致性算法(RANSAC)的运动估计算法,该方法首先使用SIFT算法对图像序列的特征点进行提取并匹配,然后使用RANSAC算法消除误匹配点并获取投影变换矩阵,从而获得图像序列间的亚像素级的运动信息;采用一组低分辨率序列图像进行试验,基于上述运动估计算法,采用迭代反投影进行超分辨率重建。试验结果表明,运动估计精度较高,重建影像具有较好的视觉效果,尤其适用于影像序列间存在旋转缩放运动的图像序列的超分辨率重建。 相似文献
12.
13.
郭俊义 《武汉大学学报(信息科学版)》2000,25(5):393-395
通过引进章动坐标系相对惯性参照系的转动角速度随时间的变化 ,导出了一个可同时解出章动和极移的地球自转方程 ,用这个方程可同时研究地球的强迫和自由转动。与现行研究地球自转的惯用方法相比 ,该方法综合性强 ,易于理解。 相似文献
14.
《Geoscience and Remote Sensing Letters, IEEE》2008,5(4):608-609
15.
GNSS卫星作为一种照射源,可与地面接收机构成天-地无源双基地雷达系统,用于海面移动目标探测。但是,海面目标(如船只)反射的GNSS信号能量微弱,常被淹没在背景噪声和干扰信号中。针对这一问题,本文提出利用目标的运动特点聚集目标回波能量的目标探测方法。首先,将船只的运动轨迹看作合成孔径,采用SAR成像技术——距离多普勒算法(range-Doppler algorithm,RDA)实现目标回波能量的压缩聚集,同时抑制干扰信号(如海面杂波)。然后,使用相位梯度自聚焦算法(phase gradient autofocus,PGA)作自聚焦处理,进一步聚集目标回波能量。通过现场试验采集的数据验证了本文算法。试验结果表明,本文方法能够同时聚集多个目标回波能量,精确地估计目标到接收机的距离,并判断目标的移动方向。 相似文献
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17.
The Doppler effect is the apparent shift in frequency of an electromagnetic signal that is received by an observer moving relative to the source of the signal. The Doppler frequency shift relates directly to the relative speed between the receiver and the transmitter, and has thus been widely used in velocity determination. A GPS receiver-satellite pair is in the Earth’s gravity field and GPS signals travel at the speed of light, hence both Einstein’s special and general relativity theories apply. This paper establishes the relationship between a Doppler shift and a user’s ground velocity by taking both the special and general relativistic effects into consideration. A unified Doppler shift model is developed, which accommodates both the classical Doppler effect and the relativistic Doppler effect under special and general relativities. By identifying the relativistic correction terms in the model, a highly accurate GPS Doppler shift observation equation is presented. It is demonstrated that in the GPS “frequency” or “velocity” domain, the relativistic effect from satellite motion changes the receiver-satellite line-of-sight direction, and the measured Doppler shift has correction terms due to the relativistic effects of the receiver potential difference from the geoid, the orbit eccentricity, and the rotation of the Earth. 相似文献
18.
反射率因子和径向速度共同约束反演多普勒雷达风场 总被引:2,自引:0,他引:2
多普勒雷达可以提供降水回波区的风场信息。为了充分运用雷达资料分析中小尺度天气过程,本文假设反射率因子在短时间内的运动满足拉格朗日守恒,提出了采用连续两次的反射率因子回波和径向速度数据共同约束的方法来反演风场,在反演过程中避免了对径向速度的分布进行假设。针对连续两个时次之间反射率回波运动中产生的不同程度的误差做了模拟风场试验,结果表明,当回波运动随机误差不超过40%时,反演结果较为可靠。另外,本文还利用此风场反演方法进行两次中尺度天气过程的实例分析。结果表明,该方法反演的风场与实际风场结构相符,具有一定的应用价值。 相似文献
19.
Yuichi Imanishi 《Journal of Geodesy》2009,83(5):455-467
The superconducting gravimeter (SG) has a long-period instrumental noise called the parasitic mode at periods around 100 s,
whose precise mechanism has not yet been identified. In this paper, another instrumental noise is detected at much higher
frequencies by analyzing the high-rate gravity channel of two SGs in Japan. This is also a parasitic oscillation, characterized
by frequencies on the order of 1 Hz and very high Q values. Detailed spectra indicate that the noise actually consists of two modes with small frequency separations. Based on
a simple theory on the rotational motions of the superconducting sphere in the gravity sensor, the observed modes are tentatively
identified as rotational oscillations of the sphere about two orthogonal axes in the horizontal plane. Interactions between
the parasitic modes are investigated using the spectra acquired on an earthquake, to conclude that the low-frequency parasitic
mode is likely to be a rotational motion of the sphere about the vertical axis. 相似文献
20.
《Geoscience and Remote Sensing Letters, IEEE》2008,5(4):573-577