Conventional SAR (Synthetic Aperture Radar) techniques only consider a single reflection of transmitted waveforms from targets. Nevertheless, today?s new applications force SAR systems to work in much more complex scenes such as urban environments. As a result, multiple-bounce returns are additionally superposed to direct echoes. We refer to these as ghost images, since they obscure true target image and lead to poor resolution. By applying Time Reversal concept to SAR imaging (TR-SAR), it is possible to reduce considerably ?or almost mitigate? ghosting artifacts, recovering the lost resolution due to multipath effects. Furthermore, some focusing indicators such as entropy (E), contrast (C) and Rényi entropy (RE) provide us a good focusing criterion when using TR-SAR
