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In this article, a unified learning-based approach is introduced to solve inverse scattering problems (ISPs) with mixed boundary conditions (BCs). The scattering behavior of hybrid dielectric and perfect electric conductors (PEC) scatterers is modeled by the T-matrix method. A rough image of the zero-order T-matrix coefficients for unknown scatterers is first reconstructed by the backpropagation (BP) method, which is then refined by an attention-assisted pix2pix generative adversarial network (GAN). The spatial attention mechanism is utilized to enforce the generator network to learn salient features of the unknown scatterers instead of the background. The adversarial training of the generator and the discriminator further enables the reconstructed image to be constrained by high-level features of reference scatterers. Numerical tests on both synthetic and experimental data verify the superior performance of the proposed method for ISP reconstructions with hybrid scatterers. It effectively expands the application scope of learning-based ISP methods to reconstruct scatterers without knowing the BCs of scatterers in advance. [ABSTRACT FROM AUTHOR]

Translation is a degree of freedom used in the analysis of random media scattering. An analytical method is presented for rotational degree of freedom in such problems. Vector addition theorem for rotation of a vector spherical wave with zero divergence has been proved through the use of a vector rotation operator. The relation between T-matrices for an object in two different concentric coordinate systems is formulated by applying the addition theorem. The relationship between the two coordinate systems is also shown by Euler angles. [ABSTRACT FROM AUTHOR]