Through-Wall Imaging With UWB Radar System - KEMT FEI TUKE
Through-Wall Imaging With UWB Radar System - KEMT FEI TUKE
Through-Wall Imaging With UWB Radar System - KEMT FEI TUKE
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2.5 <strong>Radar</strong> <strong>Imaging</strong> Methods Overview 38<br />
Stage 1 Stage 2 Stage 3<br />
Fig. 2.5.7: An example of factorisation (upper side) and the resultant hierarchy of<br />
data-sets (lower side).<br />
2.5.13 Migrations with Antenna Beam Compensation<br />
Kun Liu et al. [90] in 2002 made a research how the consideration of antenna angle<br />
beam would change computations and results in wave equation based algorithms<br />
such as Kirchhoff migration and f-k migration. They called it the effects of diplimited<br />
Kirchhoff migration and f-k migration. In praxis most measurements are<br />
done with wide beam antennas. However, not with omni-directional, but with<br />
some specific antenna flaring angel beam, that can be precisely measured. The<br />
waves that are aslant to the antennas have lower transmitted or received amplitudes.<br />
Taking into account this fact in computations some improvements can be<br />
done in the resulting image. It also decreases the computational cost in Kirchhoff<br />
migration or suppress noise in both Kirchhoff and f-k migration [90]. Dip-limited<br />
f-k migration is common f-k migration with an embedded dip filter. The diplimited<br />
Kirchhoff migration is implemented by limiting the aperture of migration<br />
operators. The dip-limited Kirchhoff migration generates additional artifacts when<br />
the dip limit is less than the maximum dip on the desired output section. These<br />
artifacts are caused by the endpoints of the migration operators and become more<br />
obvious as the dip limit is decreased. A geometric explanation as well as a synthetic<br />
experiment are described in [90]. <strong>With</strong> the same idea, however, much more<br />
from mathematical point of view Murthy N. Guddati et al. [65] came in 2005.<br />
2.5.14 Conclusion<br />
The migrations are formally divided into two main groups. Backprojection involves<br />
migration based on simple geometrical approach, whereas Backpropagation represents<br />
migrations based on wave equations. Hence, the backpropagation migrations<br />
should provide better results from physical point of view.<br />
SAR imaging, Kirchhoff migration, and Stolt migration are most often used<br />
migrations. SAR imaging and Kirchhoff migrations have almost the same compu-