The application of diffraction technology to ultra wideband synthetic aperture radars (UWB SAR) was investigated to find an optimal solution to high-quality radar imagery. The microwave imagery criterion is presented and the spatial frequency coverage is introduced to evaluate imaging systems at first. Then radar imagery is analyzed with the comprehensive consideration of the scattering mechanisms, the data acquisition system, and the image reconstruction algorithm. Theoretical and numerical results show UWB SAR exploiting diffraction technology has the potential to realize high-resolution geometric imaging and probe inherent physical properties of targets. This provides a theoretical basis for formation flight and optimization of SAR systems.