Hu Donghui

Non-linear chirp scaling algorithm for one-stationary bistatic SAR

This paper points out the non-linear property of the differential RCM along range direction in one-stationary bistatic SAR, and compares it with the monostotic case. Then it deduces out a non-linear chirp scaling factor to identify the RCM of all targets in the swath. The implementary processes of a non-linear chirp scaling algorithm for one-stationary bistatic SAR are then described detailedly. Finally, the simulating results present here validate the correctness of the algorithm.

An advanced 2-D spectrum for high-resolution and MEO spaceborne SAR

In this paper, an advanced range equation is presented for high-resolution and medium-earth-orbit (MEO) synthetic aperture radar (SAR). Besides an additional linear component, this new equation has a similar formalism to conventional hyperbolic range equation (CHRE), so is called the advanced hyperbolic range equation (AHRE). Incorporating with this additional linear coefficient and the other two parameters, the cubic Taylor series expansion of AHRE has exactly the same value as which of the actual range history. Furthermore, a two-dimensional (2-D) spectrum based on AHRE is derived, which is useful for developing efficient SAR algorithms. Simulations validate AHRE and show its advantages in highresolution and MEO spaceborne SAR cases.

A Fast Method for InSAR Phase Unwrapping Based on Quality Guide: A Fast Method for InSAR Phase Unwrapping Based on Quality Guide

Phase unwrapping is a key issue in InSAR research. As a critical step of InSAR processing, it affects the accuracy of interferometry measurement directly. The efficiency of the traditional quality-guided phase unwrapping method is low due to a great deal of sorting, espceically for large interferogram. This paper proposes a highly efficient quality-guided phase unwrapping method based on heap sort in order to solve the problem. First, the quality map is caculated according to the interferometric complex data or interferogram. Next, with the max-heap acting as the data structure of sorting, its property is maintained while deleting root node and inserting new node, and thus the sorting of quality map is accomplished and the phase can be unwrapped from high quality areas to low quality areas. The improved algorithm reduces the computational complexity greatly compared with traditional methods, which is significant in large area mapping of InSAR. At the end of the paper, the simulated and experimental results show the accuracy and the efficiency of the algorithm. Key word: Interferometric SAR (InSAR); Interferometric phase; Phase unwrapping; Quality map; Heap sort

A novel single-channel SAR-GMTI method based on defocusing shifted difference

A novel single channel SAR-GMTI method is proposed in this paper. When the azimuth mismatch filter performs compression, it induces shifted difference between the stationary and moving targets because of having different Doppler center. The proposed method employs this character to separate moving targets from stationary targets. It can produce two images by pulse compression which make use of two symmetrical mismatch filters in azimuth direction, and then cancel stationary and retain moving targets by subtracting one image from another. Compared with traditional methods, it is applicable to both low and high squint case and the detection capability is significantly improved. The simulation results validate the effectiveness of the proposed method.

Correction method for saturated SAR data to improve radiometric accuracy

In this paper, a correction method for saturated SAR data that is caused by the limited dynamic range of the analog-to-digital converter (ADC) was investigated. Since power loss due to saturation from the raw data is not the same as the power loss from the image, a correction method including two steps for the saturated SAR data was proposed. Firstly, power compensation based on raw data for distributed targets was presented. The next, compensation for the differences between power loss from image and it from raw data was performed through analyzing the relation between gain alteration of image processors and standard deviation from ADC output data. The proposed method was verified by using simulated radar data and also Radarsat-1 SAR data.

Applying chirp-modulated back-projection to very high resolution spaceborne sliding spotlight SAR data processing

This paper proposed a new approach to focus the very high resolution spaceborne sliding spotlight synthetic aperture radar (SAR) data. The main singularity of the approach is accommodating the space dependent range histories by a back projection method on reduced apertures achieved by chirp modulation method. Besides, in the range spectrum domain, a dechirp method is employed to reduce the Doppler bandwidth to be within one PRF interval. Additionally, range splitting method is employed to mitigate the range dependence of effective velocities. Furthermore, the image grid is placed on the earth surface instead of the slant range plane, and the routine geometry projection processing becomes dispensable. The proposed approach was validated by simulation results of nine point targets.