Todor Pavlov Kostadinov

SAR triangle CW LFM signal formation and imaging

Synthetic Aperture Radar (SAR) with triangle Linear Frequency Modulated (LFM) Continuous Wave (CW) is considered. Algorithms for signal formation and image reconstruction of a moving target are suggested. Three-dimensional (3-D) SAR geometry of the target presented as an assembly of point scatterers is analytically described. Mathematical expressions for distance vector determination defined from SAR to each point scatterer are derived. SAR signal model based on a triangle linear frequency modulated continuous wave emitted signal, 3-D geometry and reflectivity function of the target is derived. Image reconstruction procedure based on Fourier transform for range compression and azimuth compression is applied. SAR imaging algorithm of a moving target is suggested. Numerical experiment is carried out.

Bistatic SAR system with GPS transmitter

Bistatic Synthetic Aperture Radar (BSAR) with GPS transmitter is in a focus of consideration. Bistatic topology, satellite transmitter of opportunity and stationary receiver, combined with inverse synthetic aperture radar (ISAR) technology with GPS P code modulated waveform for imaging of a moving are presented. Kinematical equations and mathematical model of the deterministic BSAR signal are created. It is proven that the signal formation and image reconstruction can be regarded as direct and inverse space transforms. Stages of image reconstruction, including phase correction, cross-correlation range compression and Fourier transform azimuth compression are defined. The effectiveness of models and algorithms are illustrated with results of numerical experiments.

ISAR autofocusing image reconstruction of sea target

This work deals with the implementation of ISAR method to extract an image of a sea target with high resolution. Three dimensional ISAR scenario, including radar and a target of interest, is depicted in one and the same 3-D Cartesian coordinate system and duly considered. The sea target is presented as an assembly of discrete point scatteres which intensities are interpreted as an image function of the object observed. Analytical geometrical expressions to define a range distance from the radar to each point scatterer from the object space are derived. In order to realize high range resolution on the line of sight an informative linear frequency modulated waveform is applied. An ISAR signal model as a superposition of signals reflected from targets point scatterers is described and graphicaly illustrated. Image extraction from ISAR signal returns is performed by implementation of Fourier transformation on both range and cross-range coordinates. Image enhancement is accomplished by iterative polynomial focusing procedure and entropy as a cost function. In order to verify the supposed algorithm a numerical experiment is performed.

Direct signal's impact on BISAR signal formation and image reconstruction

In this work the evaluation of the direct signal impact on the process of signal formation and image reconstruction, and on the quality of the reconstructed image in Bistatic Inverse Synthetic Aperture Radar (BISAR) is discussed. Geometric description of BISAR topology with space-based transmitter and receiver, and moving target is given. Kinematic vector equations are derived. The composition of the BISAR pulse signal with linear frequency modulation (LFM) reflected from the object and direct signal from the transmitter is analytically described. Image reconstruction algorithm is suggested. Numerical experiments to verify the composed signal model and imaging algorithm are carried out.

GISAR image reconstruction based 2-D smoothed l0 norm minimization in sparse decomposition

General Inverse Synthetic Aperture Radar (GISAR) imaging algorithm based on two-dimensional (2-D) l0 norm minimization in signal sparse decomposition is discussed. GISAR geometry and kinematics are analytically described. GISAR signal model based on Linear Frequency Modulated (LFM) waveform is derived. The GISAR signal formation process is presented as a sparse decomposition in redundant Fourier basis. Image reconstruction procedure is presented as minimization of smooth norm of the image matrix. The algorithm of minimization of the number of non-zero point scatterers is thoroughly described. The results are illustrated by a numerical experiment.

Short time pulse Bistatic Forward Scattering Inverse Synthetic Aperture Radar imaging

In this work Bistatic Inverse Forward Scattering Inverse Synthetic Aperture Radar (BFISAR) concept is addressed. Geometric description of BFISAR topology with stationary transmitter and receiver, and moving target is given. Kinematic vector equations are derived. BFISAR signal mathematical model with short pulse modulation is described. It is proven that BFISAR signal formation and image reconstruction can be interpreted as direct and inverse projective operation respectively. Through Taylor expansion of the projective operator basic image reconstruction procedures, including phase correction, Fourier transform range compression and Fourier transform azimuth compression are defined. Numerical and natural experiments to verify mathematical models derived are carried out.

BSAR SIGNAL MODELING AND SLC IMAGE RECONSTRUCTION

Abstract: In this paper, a Bistatic Synthetic Aperture Radar (BSAR) signal model and Single Look Complex (SLC) image obtained by multiple satellite BSAR system are considered. Geometry and kinematics of BSAR scenario, including a BSAR satellite transmitter and multiple receivers as well as a complicated surface of observation are described. BSAR signal model based on linear frequency modulated emitted waveform and BSAR scenario is derived. Standard Fourier transformation is applied to extract an SLC BSAR image of high quality on range and cross range directions. To verify the BSAR signal model and image extraction procedure a numerical experiment is carried out.