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A time-domain inverse scattering approach using time-reversed fields for reconstructing electrical parameters of cylindrical objects based on gradient method is proposed. The approach does not require the explicit knowledge of incident fields illuminating the object and the time-reversed fields are calculated by time-reversing the equivalent current sources determined by the total fields recorded...
An inverse scattering problem of determining the electrical property of an unknown dielectric object is considered. The electromagnetic wave generated by an impressed electric current with a short duration time illuminates the dielectric object. The measured data of the total field, the sum of the incident and scattered fields, over an observation surface S is used to reconstruct the electrical property...
Time reversal imaging methods have received considerable attention since they yield accurate location estimate of point scatterers. Up to now, most time reversal methods have focused on detection and localization of point-like or small targets [1, 2] and not dealt with estimation of electrical parameter profile of scatterers. We have proposed a gradient based time-reversal imaging technique which...
Forward-Backward Time-Stepping Method (FBTS method) is a technique to solve time domain inverse scattering problem. An incident pulse is radiated to unknown object. The scattering wave is measured at M points. A similar measurement is carried out at N different incident points. Total number of measured data is M × N. In FBTS method, the estimated field is calculated by FDTD method. The number of calculation...
On May 24, 2014, ALOS2 was launched. ALOS2 is the follow-on satellite of ALOS and has the L-band Synthetic Aperture Radar (PALSAR2). PALSAR2 provides an image with the higher resolution(3m) and wider swath(50km) in high resolution mode as compared with the image of former L-band SAR (PALSAR). Since PALSAR2 has a function of polarimetric observation by utilizing horizontal (H) and vertical (V) polarized...
A new forward-backward time-stepping (FBTS) method using gradient-based optimization method has been proposed for inverse scattering problems. This method is based on the field equivalence principle and does not require the explicit knowledge of the incident field. Due to the nonlinearity of the inverse scattering problem, the solution based on gradient methods often gets trapped into a local minimum...
An X-band airborne SAR, Pi-SAR2, has been developed by NICT. It can make polarimetric and interferometric observation with very high spatial resolution of 0.3m. Since 2013, NICT has carried out collaborating observations on research proposals selected for the Pi-SAR2 Research Announcement. Polarimetric SAR data analysis is a key issue among them, therefore we have made polarimetric calibration in...
In this paper, the retrieval of sparse defects within known two-dimensional structures is addressed. A Bayesian Compressive Sensing technique has been developed to determine the differential induced currents thanks to a proper definition of an inhomogeneous Green's function enabled from the a-priori knowledge of the unperturbed structure. Successively, a contrast source inversion method has been applied...
The solution of linear microwave imaging problems is considered in this work through innovative classes of Compressive Sensing (CS) methods. More in detail, the formulation of the inversion process in transformed domains with sparseness-regularized formulations is considered. Representative numerical examples illustrating the potentialities and limitations of the arising CS inversion approaches are...
The analysis of the effects on the power pattern radiated by reflector antennas in presence of localized defects (also called bumps) of the parabolic surface is addressed by means of an innovative analytic strategy. The bump depths are supposed unknown or estimated with a given tolerance such that their deviations from the nominal surface can be expressed as intervals of values. The upper and lower...
The retrieval of the dielectric characteristics of 2-D objects buried in a lossy half-space from Ground Penetrating Radar (GPR) measurements is dealt with. The proposed imaging algorithm is able to effectively mitigate the effects of both non-linearity and ill-posedness of the inversion problem through a multi-scaling deterministic approach based on a Conjugate Gradient minimization (IMSA-CG), while...
The analysis of the tolerance effects on the radiated power pattern caused by the fabrication errors in the printing of the microstrip patches of reflectarrays is addressed through a method based on the Interval Analysis and the arithmetic of intervals. The dimensions of the microstrip patches are defined as intervals of values including the tolerance errors and the mathematics of intervals is exploited...
This paper presents an innovative microwave imaging technique for detecting defects in dielectric or conductive media developed through the Bayesian Compressive Sensing theory. Thanks to the a-priori knowledge of the medium unaffected by defects, the inversion problem is formulated as the estimation of the sparse differential equivalent currents within the support of the defects. The strategy has...
A novel gradient-based inverse scattering method for imaging inhomogeneous objects from time-domain data of only total electric field is presented. Unlike most inverse scattering methods, the proposed method does not require the explicit information of the incident field illuminating a region of interest. Numerical simulations demonstrate the effectiveness of the method.
A time-domain inverse scattering approach using time-reversed fields for reconstructing electrical parameters of cylindrical objects has been proposed in a previous work. The approach does not require the explicit knowledge of incident fields illuminating the object. The cost functional represented in terms of the time-reversed fields was minimized by a genetic algorithm (GA). In this paper, we propose...
A time-domain inverse scattering approach based on the field equivalence principle is developed for reconstructing the electrical parameters of an unknown object using the tangential components of the electric field measured in presence and absence of the object. Numerical simulations demonstrate the effectiveness of the approach.
A time-reversal approach to reconstructing the electrical parameters of an inhomogeneous object from measured total field data is considered. It is shown that the approach does not require the information of the incident field in the region of interest enclosing the object when the primary source is placed outside of the region. Numerical simulations are performed to validate the effectiveness of...
This paper considers a fast calculation of adaptiven-on-negative eigenvalue-decomposition (ANNED). ANNED is one of useful polarimetric decomposition techniques and provides valuable information for remote sensing from measured covariance matrix. It has a disadvantage to take long time to estimate the decomposition parameters. To overcome this problem, the generalized eigenvalue problem has been applied...
In this paper, time-domain inverse-scattering technique referred to as Forward-Backward Time-Stepping (FBTS) method is applied to microwave imaging breast cancer detection. The FBTS algorithm is implemented in C++ language executed in a single computer by developing the time domain form of the FDTD. The ability to detect as small as 4mm of the embedded tumour and reconstructing the image in two-dimensional...
A time-reversal approach is developed for reconstructing electrical parameters of a stratified slab from time-domain reflection and transmission data. The impressed source as well as the equivalent sources corresponding to the measured reflected and transmitted fields are time-revered. Numerical simulations are performed to reconstruct an image of a stratified dielectric slab.
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