Range Coherence Factor for Down Range Sidelobes Suppression in Radar Imaging Through Multilayered Dielectric Media

In radar imaging applications through layered dielectric media, an antenna array with a limited operating frequency bandwidth at the low end of the microwave band is usually employed to probe the target space of interests. As a result, the focused radar imagery is characterized by severe sidelobes in the down-range direction, which leads to the degradation of the image quality. Several techniques, such as windowing and apodization filtering combined with phase coherence factor (PCF) filtering, have been reported to suppress the down-range sidelobes. However, these approaches either expand the main lobe width or are sensitive to parameter tuning. In this paper, by investigating the distribution characteristics of the down-range sidelobes among sub-frequency radar imageries, a robust and efficient range coherence factor (rCF) technique is proposed to suppress the down-range sidelobes in the focused radar imagery. The performance of the proposed approach is assessed by the finite-difference time-domain (FDTD)-based numerical simulations as well as onsite experiments to verify its sidelobes' reduction capabilities.