Harmonic transponders differ from linear transponders by offering higher clutter mitigation and especially when the transponders are placed on highly reflective items or present in reflective environments. This paper exploits the inherent non-linearity in order to clearly sense and localize these transponders. The employed transponder is completely planar with a small footprint of 2 mathbf{cm} times 3 mathbf{cm} Furthermore, the transponder consists of two bowtie dipoles that are directly matched to the harmonic generation element at fundamental 2.45 GHz frequency and also at the corresponding second harmonic 4.9 GHz frequency. In this paper, the inherent non-linearity sensing is exploited with Synthetic Aperture Radar (SAR) in a highly cluttered environment. The proposed method is able to provide precise information along range and cross-range directions.