Bidirectional reflection distribution function modeling (BRDF) for terahertz diffuse scattering analysis of dielectric rough targets

This paper presents an optical method to determine the scattering characteristics of dielectric rough targets in the terahertz band. Based on the complex permittivity of alloy Al (Aluminum) and painted Al obtained from the reflectance spectra, the analytical bidirectional reflection distribution function (BRDF) spectra of rough surfaces are simulated using physical optics. The effects of surface roughness, complex permittivity, incident angle, and wavelength are analyzed. With the optimization of artificial immune network genetic algorithms, it is demonstrated that the optimized five-parameter BRDF empirical model fits the analytical BRDF spectra over a wide range of incidence angles. Then, the radar cross section (RCS) of electrically large targets can be simulated by the relationship between the differential scattering coefficient and BRDF. The obtained RCS of the rough sphere from optimized BRDF model is in good agreement with the numerical analysis that was obtained. The proposed method is suitable for obtaining the scattering properties of large dielectric targets with different surfaces compared with traditional high-frequency electromagnetic (EM) techniques. The backscattered and bistatic terahertz RCS of a cylinder, cone and NASA almond are simulated. The proposed method shows the potential for the application of BRDF in the areas of scattering analysis and remote sensing.