Showing papers by "Mengdao Xing published in 2006"

Divison of Imaging Intervals and Selection of Optimum Imgaging Time for Ship ISAR Imaging Based on Measured Data

Abstract: In this paper an Inverse Synthetic Aperture Radar (ISAR) imaging algorithm for ship targets based on the division of imaging intervals and the selection of optimum time is proposed. The relative motion of a ship on the ocean wave can be broken into three components, namely pith, roll and yaw, which makes the Doppler frequency vary with the slow time. So during the whole slow time the echoes are not linear frequency modulation (LFM) signals any more. Under this condition the division of the imaging intervals and the selection of the optimum imaging time during the considered imaging interval are of great importance for ISAR imaging of ship targets. The imaging results of the measured data demonstrate the effectiveness of the proposed approach.

A new method of motion error extraction from radar raw data for SAR motion compensation

Abstract: Due to the presence of atmospheric turbulences, airborne SAR raw data may be affected by deviations of the platform from an ideal straight line Additionally, being rather expensive, the Inertial Navigation System (INS) and the Global Position System (GPS) do not always provide desired accuracy and reliability This paper presents a solution for aircraft motion error extraction from radar raw data Based on the derived model, the acceleration in line of sight (LOS) direction is separated into range space invariant and variant components The main idea is to extract these components of the acceleration from radar raw data Then the displacement of the platform in LOS direction can be extracted and compensated In addition, since the system under consideration in this paper operates with a constant Pulse Repetition Frequency (PRF), the motion error introduced by forward velocity variation should be considered This paper also presents a solution for compensating this motion error Finally, we present results on real data aimed at validating the proposed methods

Suppression of Azimuth Ambiguities with Constellation of Micro-satellites

Abstract: To achieve wide-swath and full azimuth resolution in space-borne Synthetic Aperture Radar (SAR), a space-borne radar usually utilizes low Pulse Repetition Frequency (PRF) with a small aperture in azimuth. Consequently, the azimuth ambiguities are inevitable. As one solution to this problem, Space domain filter can be utilized to remove the azimuth ambiguities based on the configuration of micro-satellites distributing along track. In this paper, an innovative method is proposed to simplify the calculation of the filter weight vectors. Simulation shows the validity of the method.

Synthetic Bandwidth Method Integrated with Characteristics ofSAR

Abstract: Stepped-frequency subpulse signals are widely used to obtain ultra-high range resolution The stepped-frequency subpulse signals can be combined to one single signal with high bandwidth by using synthetic bandwidth methods In practical SAR imaging motion error and the time delay of echo signal must be considered before applying the available synthetic bandwidth methods This paper presents a method in which motion compensation and compensation in Doppler domain are integrated with time domain synthetic bandwidth method in order to get high quality SAR image

An Effective Approach to Ground Moving Target Imaging for Single Channel SAR System

Abstract: Based on the envelopes and the characteristics of Doppler spectrum of returns in single channel synthetic aperture radar (SAR) systems a method is proposed, which adopts two order Keystone Transform to adjust the range curvature of echo data, then range walk rates of echoes' envelopes are estimated to make some adjustments of walk and the Doppler parameters of moving targets are obtained through analyzing the Doppler spectrum of the moving targets At last the images and positions of ground moving targets are gained, which make it possible that the moving targets can be indicated in right locations in SAR image In addition the key motion parameters of moving targets can be estimated by the relationship between the Doppler parameters and motion parameters of ground moving targets The results of the measured data show that this method can image ground moving targets and estimate motion parameters effectively

A New Algorithm for Sparse Aperture Extrapolation

Abstract: An algorithm for estimating full aperture with sparse data is proposed in this paper. For wide vacant aperture in sparse data, by measuring sparse data actually, accurate sparse data frequency domain energy distribution estimate can be obtained with parametric approaches. With estimated power spectrum as prior information, minimum weighted norm as the restraint, underdetermined equations are solved to interpolate vacant aperture, thus wide aperture data segment estimate is obtained. This algorithm can be effectively applied to ISAR imaging in sparse data. Resulting simulation and actual data processing results confirm validity of the proposed algorithm