  In this work, an optimization-based inverse design method is provided for
multi-input multi-output (MIMO) metastructured devices. Typically,
optimization-based methods use a full-wave solver in conjunction with an
optimization routine to design devices. Due to the computational cost this
approach is not practical for designing electrically-large aperiodic
metastructured devices. To address this issue, a 2-D circuit network solver
using reduced order models of the metastructure's unit cells is introduced. The
circuit network solver is used in conjunction with a gradient-based
optimization routine that uses the adjoint variable method to solve large-scale
optimization problems like those posed by metastructured devices. To validate
the inverse design method, a planar beamformer and an analog signal processor
for aperture field reconstruction are designed and validated with full-wave
simulations.
