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Liu J.,Chinese Academy of Sciences | Liu J.,CAS Institute of Electronics | Hong W.,National Key Laboratory of Microwave Imaging Technology | Hong W.,CAS Institute of Electronics
Journal of Electronics | Year: 2012

Range-Doppler (RD) method and Reverse-Range-Doppler (RRD) method are combined together to achieve automatic geocoding of Synthetic Aperture Radar (SAR) image quickly and accurately in the paper. The RD method is firstly used to locate the four corners of the image, then the other pixels of the image can be located by Reverse-Range-Doppler (RRD) method. Resampling is performed at last. The approach has an advantage over previous techniques in that it does not require ground control points and is independent of spacecraft attitude knowledge or control. It can compensate the shift due to the assumed Doppler frequency in SAR image preprocessing. RRD simplifies the process of RD, therefore speeds up the computation. The experimental results show that a SAR image can be automated geocoded in 30 s using the single CPU (3 GHz) with 1 G memory and an accuracy of 10 m is attainable with this method. © 2012 Science Press, Institute of Electronics, CAS and Springer-Verlag Berlin Heidelberg.

Tan H.,CAS Institute of Electronics | Tan H.,University of Chinese Academy of Sciences | Tan H.,Chinese Academy of Sciences | Hong J.,CAS Institute of Electronics | And 2 more authors.
IEEE Geoscience and Remote Sensing Letters | Year: 2015

A compact polarimetric (CP) synthetic aperture radar (SAR) has an advantage of reconstructing quad-polarimetric (quad-pol) information from measured dual-polarized scattering vectors. In order to fully explore CP data, calibration of CP measurements is important. However, among different system errors, the crosstalk on transmit is not possible to be corrected in measured scattering vectors even when it is already estimated and known. Except scattering vectors, reconstructed quad-pol data are widely used. Three reconstruction algorithms have been published in the literature: one by Souyris et al., a refined algorithm by Nord, and another refined one by Collins et al. However, the removal of transmit crosstalk is still left unresolved. In this letter, we proposed a calibration algorithm to correct the transmit crosstalk in reconstructions of quad-pol data from CP data. We conducted simulations with fully polarimetric Advanced Land Observing Satellite Phased Array L-band SAR data. Simulation results confirmed that the algorithm performed effectively and stably under certain conditions. © 2015 IEEE.

Liu J.,Chinese Academy of Sciences | Liu J.,CAS Institute of Electronics | Liu J.,University of Chinese Academy of Sciences | You H.,Chinese Academy of Sciences | And 3 more authors.
Wuhan Daxue Xuebao (Xinxi Kexue Ban)/Geomatics and Information Science of Wuhan University | Year: 2013

A modified orbit algorithm with sparse ground control points (only three points) for high accuracy geo-rectification of space-borne SAR image is proposed, which is based on range-doppler position model and high precision orbit data of GPS. The algorithm decreases the number of ground control points through simplifying the orbit parameter model, so it can improve the work efficiency on the basic of high accuracy correction.

Zhang Y.,University of Chinese Academy of Sciences | Zhang Y.,CAS Institute of Electronics | Zhang Y.,Chinese Academy of Sciences | Ding C.,CAS Institute of Electronics | And 6 more authors.
Journal of Infrared, Millimeter, and Terahertz Waves | Year: 2012

With the development of several High Resolution (HR) Synthetic Aperture Radar (SAR) systems, many special phenomena appear in the SAR image, especially for the SAR image with millimeter wave. We firmly believed that every detail in the SAR image should have its own special mechanisms and these details may provide some key clues for us to build up the frame work on understanding the SAR image. The synthetic aperture is one of the important particularities about SAR, and the radar is moving during the data is collected, which leads many special phenomena in the SAR image; one of these is the shadow with blurred boundary. In this work, the effect on the shadow region in the SAR image by synthetic aperture is expanded on. The blurred boundary of the shadow is analyzed using imaging formation theory, and the Quadratic Phase Errors (QPE) brought by the synthetic aperture progress is deduced for the first time, which builds up the relationship between the parameters of the shadow caster and the behavior of the shadow in the SAR image. It is found that the QPE is approximately a linear function of the height of the shadow caster. Furthermore, an approach for shadow enhancement based on height variant phase compensation is proposed and it could provide a better effect on shadow enhancement than the traditional technique called Fixed Focus Shadow Enhancement (FFSE), which is proved by theoretical analysis and experiments. Based on the analysis, some typical application of the about the shadow region. It is expected that the work in this paper could be some helpful for the SAR image understanding and the microwave imaging with high resolution. shadow in SAR image is designed and some mini-SAR image with Ku-band is analyzed about the shadow region. It is expected that the work in this paper could be some helpful for the SAR image understanding and the microwave imaging with high resolution. © Springer Science+Business Media, LLC 2012.

Liu X.-M.,CAS Institute of Electronics | Liu X.-M.,University of Chinese Academy of Sciences | Gao W.-J.,CAS Institute of Electronics | Gao W.-J.,National Key Laboratory of Microwave Imaging Technology | And 2 more authors.
2010 9th International Symposium on Antennas Propagation and EM Theory, ISAPE 2010 | Year: 2010

An integrated beam synthesis algorithm is presented to optimize the multiple beams of variable look-angle SAR antenna. With an iterative solution scheme of improved projection matrix algorithm, the amplitude excitations (common to all beams) and the phase of such excitations (corresponding to each radiated beam) are determined simultaneously. Antenna beams are controlled by phase only in SAR system. The sample application of multiple beams SAR antenna design is given to illustrate the effectiveness of the presented algorithm. And the noise-equivalent sigma-zero ( NEσ0 ) of SAR system is improved as well. ©2010 IEEE.

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