Bidirectional Scattering Distribution Function of Electrically Large Distributed Rectangular Slots

Electrically-large slot structures are common in building facades which are of great interest in scattering modeling for remote sensing and wireless communication applications. Existing models are often of high computational complexity and not directly integratable with ray tracing simulation engine. This article develops a dedicated bidirectional scattering distribution function (BSDF) model of wall surface with electrically-large distributed rectangular slots. It is derived mainly based on ray theory. The incident wave in one single rectangular slot is represented as parallel rays whose scattering path are analytically derived including the number of hops (NoH) and the path length. The diffuse scattering effect is modeled using the coherent spatially varying (CSV) BSDF of finite-size rough surface. The depolarization effect caused by oblique incidence is analytically formulated. The proposed BSDF model is validated against measurement data collected using an in-house developed FUSAR-Rail field scattering measurement system. Comparison with the measured scattering coefficient of two typical wall surfaces demonstrates the correctness and efficacy of the proposed method. It reveals the scattering mechanism of slot structures in a more physically interpretable way.