In this paper the phase shift migration based Syn- thetic Aperture Radar (SAR) is described and applied on radar imaging for dual polarized ground penetrating radar system (GPR). Conventional techniques for SAR imaging focusing use the matched filter concept and convolve the measurement data with a filter impulse response (convolution kernel) which is modified by the range. In fact, conventional techniques for SAR imaging technique can be considered as ray-tracing based SAR imaging technique. It is an efficient technique to obtain focused radar images, when the medium is homogeneous so that the rays of EM wave propagation can be treated as straight lines. However, in case of layered materials the waves are refracted on the interface between two different materials. In contrast, phase shift migration based SAR imaging technique is through EM field extrapolation by phase shift to obtain the reflected EM intensity and radar imaging of scatterers' reflectivity in the radar illumination area. Although EM wave is refracted on the interface of different materials, the EM wave phase is unchanged. Compared to conventional SAR imaging technique, phase shift migration based SAR imaging approach is more suited to obtain focused radar subsurface imaging for GPR systems. In this paper the phase shift migration approach is applied to experimental data as well as practical measurement data. Meanwhile, a background removal algorithm and a spreading and exponential correcting technique is applied to improve the achievement. The presented focused subsurface and scatters radar imaging results show that phase shift migration based SAR technique is satisfied for radar subsurface imaging and inhomogeneous medium imaging.
