FFT-Accelerated 3-D Near-Field Radar Image Generation for Objects Over Rough Surfaces

Conventional 3-D near-field radar image simulation requires electromagnetic (EM) scattering data collection over a densely sampled frequency-azimuth–elevation sector, resulting in burdensome or even impractical computational complexity. In this article, a fast Fourier transform (FFT)-accelerated 3-D near-field radar scattering image generation technique is proposed for objects over rough surfaces, applicable at arbitrary observation angles. A closed-form expression for the 3-D spatially variant point spread function (SVPSF) is derived to directly calculate near-field image-domain contributions from ray tubes traced using the multipath model enhanced shooting and bouncing rays (MP-SBRs). The multiple scattering effect is addressed by developing a spatial mapping process. The 3-D radar image formation is formulated as a convolution integral, allowing the FFT-acceleration scheme to significantly reduce the computational complexity. Moreover, the 3-D resolution equations are derived and used to evaluate radar image quality. Simulated radar images are compared with both measured and simulated counterparts by a conventional technique to demonstrate the high fidelity and efficiency of the proposed technique.