Zhang Changyao

Research on deceptive jamming technologies against SAR

Synthetic aperture radar (SAR) has its own special features different from conventional radar. It has high processing gain, so jamming to SAR is more difficult than that to conventional radar. Jamming to SAR finds its important usage in some military scene. In this paper, the basic principle of the SAR deceptive jamming and the model of the jamming signal are discussed, and the simulations are made. Finally, two criterions used to evaluate jamming effectiveness are provided. The jamming effectiveness is checked up used these criterions by computer simulation.

High resolution dual channel receiving SAR compensation technique

This paper presents the theory of dual-channel receiving Synthetic Aperture Radar (SAR) and internal calibration. Using the data of an airborne high resolution SAR demonstrate System collected in May 2006, the internal calibration error and amplitude & phase errors are analyzed. The raw data is compensated by internal calibration data to improve range compression quality compared to auto-focus method compensation. The image of synthesized dual channel data is performed. With the internal calibration and the dual-channel amplitude & initial phase errors compensation, the quality of SAR image can be improved dramatically.

Algorithm of target classification based on target decomposition and support vector machine

Since Huynens original work, there have been many other proposed target decomposition theorems. In this paper, we provide a review of the different approaches used for target decomposition theory in radar polarimetry and classify three main types of theorems: those based on Mueller matrix, those using an eigenvector analysis of the coherency matrix, and those employing coherent decomposition of the scattering matrix. Support vector machine (SVM), as a novel approach in pattern recognition, has demonstrated a success in many fields. Here we first extract scattering mechanisms of radar targets by target decomposition and color composite. Then we propose a new algorithm of target classification by combining target decomposition and support vector machine. We conduct the experiment on the polarimetric synthetic aperture radar data. Experimental results show that: it is feasible and efficient to target classification by designing SVM classifiers using target decomposition, and the effects of kernel functions and its parameters on the classification efficiency are significant.

A Real-time signal processing method for air-born three-channels GMTI

In this paper, we briefly introduced the performance of several GMTI systems at first. After that, we prompted a method based on CSI algorithm for air-born three-channels GMTI signal processing, gave out the processing diagram of this method, analyzed the principle of cluster suppress, present an adaptive phase compensation method for each channel based on the minimum power criterion and analyzed the locating and velocity-estimation problem of moving targets. The presented method, which has been applied in actual furnishment, turned out to be efficient.

Range-Doppler Approach for Calibration and Location of Air-borne SAR Image

This paper investigates calibration and location of air-borne synthetic aperture radar (SAR) image without ground control points (GCPs). The position of each pixel in the image lie on the geometric relationship between antenna and each scatter cell. In order to reduce the reliability on the stability of flying attitude of the airplane and improve the real-time performance of imaging algorithm, time-domain sub-aperture imaging algorithm is often used in air-borne SAR in practice when the range and azimuth resolutions are not too high. It can obtain the Doppler frequency of each pixel in the image and lay the foundation for the range-Doppler location approach, which obtains coordinates of each pixel in SAR image by means of slant range and Doppler equations. The effectivity of the location approach is validated by simulation experiment and flying trial

Interferogram Phase Noise Suppressing using Nonlinear Partial Differential Equation

The phase noise-suppressing method applied on the interferogram of interferometric synthetic aperture radar (InSAR) is studied. Filtering phase noise in an interferogram is an important aspect in InSAR data processing. But any improper altering of the wrapped phase may influence the quality of derived DEM because the interferometric phase contains the topographic information. Therefore, one of the difficulties in phase noise filtering is how to remove the noise and preserve the spatial resolution effectively. In this paper, an adaptive approach based on nonlinear partial differential equations (PDE) is presented for removing the noise in the interferogram. Finally, this approach is compared with some existing approaches for InSAR noise filtering and the experimental results by processing spaceborne and airborne data are used to confirm that the method is more effective in reducing noise in the interferogram

A New Algorithm of Target Classification Based on Maximum and Minimum Polarizations

The polarization signature of a given pixel in a radar image represents scattering mechanisms from various scattering elements. This paper presents an analysis of maximum and minimum polarizations of five kinds of polarization signatures: co-polarized, cross-polarized, completely polarized, completely unpolarized, and total available power signatures. We propose a new algorithm of target classification based on these maximum and minimum polarizations, then, conduct the experiment on the measured polarimetric SAR data. Experimental results show that this algorithm is robust to pixel-by-pixel target classification in radar images

Channels equalizing and calibration technology of moving target detection for multi-phase centers receive system

With the rapid developing of synthetic aperture radar (SAR) in recent year, multi-channel receive technology is widely applying in wide-swatch SAR, high resolution SAR, GMTI, InSAR, multi-band and multi-polarization SAR. In this paper, have a deeply discussion on equalizing between channels in wideband multi-receive aperture system when amplitude imbalance and phase non-uniform. Take a three receive aperture GMTI system as example, detail process is present, step by step from GMTI system design block diagram to final processing result. Measured data processing results validate effectiveness of the method.

Study of synchronization between geostationary illumination and bistatic reception

Distributed synthetic aperture radar (SAR) system has been in the direction of the study about SAR. Its a new type of SAR system that the transmitter based in geostationary orbit, and the receiver borne on airplane at the same time. In this paper, we briefly introduced the bistatic SAR system between geostationary satellite and airplane. The forming of the system is giving, and the synchronization in the bistatic SAR system is discussed. In the end, some result of the analyzing is giving.