Scattering and Imaging of Nonlinearly Loaded Antenna Structures in Half-Space Environments

The electromagnetic scattering responses of nonlinearly loaded antenna structures excited by single-tone or multi-tone incident fields are considered in the frequency domain by employing a combination of the method-of-moments and a harmonic balance technique. Subsequently, standoff detection and localization of the scatterers in the presence of a half space is demonstrated with a subspace imaging procedure by exploiting the steady-state, multistatic harmonic scattering responses collected over an aspect-limited aperture. The attenuation rates of the harmonic scattered fields as a function of sensing range are investigated. The Green's function vector in the imaging functional is derived efficiently with the application of second-order-accurate asymptotic propagation techniques, and near-field imaging performance for single and multiple targets is also examined in the presence of noise and linear clutter. This study is intended to provide an analysis and simulation framework needed to facilitate the development of a complementary nonlinear detection capability for an existing near-ground, forward-looking linear imaging radar system.