Shiqi Xing

The Interferometry Phase of InSAR Coherent Jamming with Arbitrary Waveform Modulation

This paper focuses on the interferometry phase of an active coherent jamming in InSAR (Interferometry Synthetic Aperture Radar) images. Based on the signal models of coherent jammer, the jammings imaging results are derived by employing the Omega-K algorithm. By comparing the imaging results of InSARs two channels, the jammings interferometry phases for both working modes, the single-pass and repeat-pass modes, are proved to be constants. And the values of the interferometry phases are determined by the jammers geometry position relative to InSAR baseline, but independent of the jammings waveform modulation and its background terrain.

THE "SLOPE" EFFECT OF COHERENT TRANSPONDER IN INSAR DEM

Although a Coherent Transponder (CT) is widely utilized in the field of Synthetic Aperture Radar (SAR), its Digital Elevation Model (DEM) has not yet been well studied for Interferometry SAR (InSAR). Based on the fact that the interferometry phase is a constant for CT with single transmit antenna, this paper mainly focuses on InSAR DEM induced by CT. The decorrelation effect in the intersection region of CT and natural terrain is researched in detail to support the analysis of CT’s phase-unwrapping. The most important property, which makes DEM of CT unique, is found to be the “slope” effect. The incline angle of “main slope” of DEM is verified to be determined only by the depression angle of InSAR baseline, whereas the incline angles of the “subordinate slopes” are affected by all the geometric parameters of InSAR baseline. Finally, all the incline angles are independent of CT’s waveform modulations, since the modulations have no contribution to the interferometry phase.

Three-Dimensional Reconstruction of Man-Made Objects Using Polarimetric Tomographic SAR

The growing interest in 3-D reconstruction of targets, particularly man-made objects, has made synthetic aperture radar (SAR) tomography a hot topic in recent years. It obtains a 3-D reflectivity map by coherently processing multiple images acquired from slightly different views. This paper investigates the use of polarimetric tomographic SAR to reconstruct 3-D images of man-made objects and proposes a polarimetric 3-D reconstruction technique, based on the multiple-measurement vector compressive sensing (CS) (MMV-CS) model and Tikhonov regularization theory. The main feature of the technique is that of allowing joint reconstruction of polarimetric 3-D reflectivity maps with high resolution. For X-band tomographic SAR, we demonstrate that the phase error induced by an array element error is severe enough to prevent data focusing and propose a phase calibration technique employing prominent scatterers to adapt the proposed technique to practice. To check the plausibility of our algorithms, a ground-based SAR system is introduced, and high-resolution 3-D images obtained by processing the real collected data are presented. As special cases of the new proposed technique, both the Tikhonov regularization and the MMV-CS method reconstruct the targets successfully and give an accurate estimate for the vehicle size. Compared to the Tikhonov regularization method, the MMV-CS technique exhibits much better superresolution power and lower sidelobe level. The advantage of the MMV-CS technique over the single-measurement vector CS technique is also demonstrated, and the phase calibration algorithm is verified.

AN EFFICIENT SAR JAMMER WITH DIRECT RADIO FREQUENCY PROCESSING (DRFP)

DRFM (Digital Radio Frequency Memory) is now widely utilized by modern radar jammers due to its high e-ciency in jamming generation. However, its jammer structure is somewhat complex, since the up-conversion and down-conversion processes must be included. This paper proposes a new Synthetic Aperture Radar (SAR) jammer architecture utilizing Direct Radio Frequency Processing (DRFP), wherein both the up-conversion and down-conversion modules can be excluded. DRFP has a very compact hardware structure which employs Direct Digital Synthesizer (DDS), phase shifter, and delay lines for jamming modulation. Finally, the performances of DRFP are shown by both the inner-fleld test and a rail-way SAR experiment to be rather efiective in jamming generation.

IMAGING ENHANCEMENT OF STEPPED FREQUENCY RADAR USING THE SPARSE RECONSTRUCTION TECHNIQUE

Based on the observation that sparsity assumption is well satisfled in the synthetic aperture radar (SAR) imaging applications, there is increasing interest in utilizing compressive sensing (CS) in SAR imaging. However, there are still several problems which should be concerned in CS-based imaging approaches. Firstly, inevitable noise and clutter challenge the performance of CS algorithms. Secondly, the super-resolving ability of CS algorithms is not su-ciently exploited in most cases. Thirdly, nonideal characteristics of mutual coherence afiect the performance of CS algorithms in complex scenes. In this paper, a novel CS imaging framework is proposed for the purpose of improving the imaging performance of stepped frequency SAR. Meanwhile, a super-resolving imaging algorithm is proposed based on the nonquadratic optimization technique. Simulated and rail SAR measured data are applied to demonstrate the efiectiveness of the novel framework with the proposed super-resolving algorithm. Experimental results validate the superiority of this method over previous approaches in terms of robustness in low SNR, better super-resolving ability and improved imaging performance in complex scenes.

Comment on "Orientation Angle Preserving A Posteriori Polarimetric SAR Calibration"

This paper is comment on “Orientation Angle Preserving A Posteriori Polarimetric SAR Calibration”.

Polarimetric 3D reconstruction of manmade objects

A new polarimetric tomography technique based on compressive sensing is proposed in this paper for the applications such as 3D reconstruction of man made target. Compared to the existing methods, the advantages of this new technique are those of preserving full image resolution, no model order selection procedure, high resolution, and low sidelobe artifacts. The effectiveness of the technique is demonstrated by processing real data collected by ground rail SAR.

A model incorporating orientation angle shift effect for polarimetric SAR calibration

The various applications of polarimetric SAR data have brought to the fore questions of polarimetric calibration. Most polarimetric calibration methods based on distributed targets employed reflection symmetry assumption, which might be inconsistent with the truth due to a possible orientation angle shift, and therefore would skew the polarimetric signatures of targets. In this paper, a model incorporating orientation angle shift effect is introduced to characterize the POLSAR data, and a numeric algorithm is presented. The proposed calibration method can preserve the orientation angle information precisely. Simulations and real SAR data experiments are performed to test the proposed method.

The performance analysis of up and down LFM based on multi-pulsed simultaneous polarimetric measurement technique

Polarimetrie measurement is the base of obtain of radar polarimetrie information, and the pattern of polarimetrie measurement and the selected waveform have an important influence on it. In this paper, a briefly introduction about the commonly interleaved-pulsed polarimetric measurement technique and the simultaneous-pulsed polarimetric measurement technique is presented. The ambiguity function and the waveform isolation function of up and down LFM signal have been studied based on multi-pulsed simultaneous polarimetric measurement technique in this paper, the theory derivation and the simulation experiment show the ambiguity function of the waveform is determined by the time-band width product and the waveformisolation is the function of the time-band width product, the waveform have a well performance in the doppler toleration.

On the performance comparisons of several sparse reconstruction algorithms

It is hard to choose one appropriate sparse reconstruction algorithm from multiple existing algorithms in different occasions. Being aware of this difficulty, four typical sparse reconstruction algorithms are studied to present comprehensive performance evaluations in terms of reconstruction accuracy, super-resolution ability and noise immunity, and it is found that the BCS algorithm performs best in noise immunity, while the Lp-norm algorithm has an outstanding performance in super-resolution ability.