#AWA IMANI COUPLE PATCH#

#AWA IMANI COUPLE PATCH#

Each plasmonic patch antenna can be accurately modeled as a polarizable, radiating, magnetic dipole. We compute the reflectance properties of a metasurface that consists of a doubly periodic array of patch nanoantennas strongly coupled to a metallic film. To confirm the validity of our model, we simulate measurements and scene reconstructions with a virtual multiaperture imaging system operating in the K-band spectrum (18-26.5 GHz) and compare its performance with an experimental system.

Alternatively, fields measured from actual metamaterial samples can be decomposed into a set of effective dipole radiators, allowing the performance of actual samples to be quantitatively modeled and compared with simulated apertures. The dipoles used in the model can have arbitrarily assigned polarizability characteristics. Here, we introduce a forward model in which the metamaterial elements are approximated as polarizable magnetic dipoles, excited by the fields propagating within the waveguide. To reliably predict the imaging performance of such an aperture prior to fabrication and experiments, it is necessary to have an accurate forward model that predicts radiation from the aperture, a model for scattering from an arbitrary target in the scene, and a set of image reconstruction approaches that allow scene estimation from an arbitrary set of measurements. The generic form of the aperture is that of a parallel plate waveguide, in which complementary metamaterial elements patterned into the upper plate couple energy from the waveguide mode to the scene. Recently, a frequency-diverse, metamaterial-based aperture has been introduced in the context of microwave and millimeter wave imaging. The dipole description provides an alternative language and computational framework for engineering metasurface antennas, holograms, lenses, beam-forming arrays, and other electrically large, waveguide-fed metasurface structures.

With the effective polarizabilities of the metamaterial elements accurately determined, the radiated fields generated by a metasurface antenna (inside and outside the antenna) can be found self-consistently by including the interactions between polarizable dipoles. Extending the polarizability extraction technique to higher order multipoles, we confirm the validity of the dipole approximation for common metamaterial elements. We demonstrate these methods on several variants of waveguide-fed metasurface elements, finding excellent agreement between the two, as well as with analytical expressions derived for irises with simpler geometries. The first method invokes surface equivalence principles, averaging over the effective surface currents and charges within an element to obtain the effective dipole moments the second method is based on computing the coefficients of the scattered waves within the waveguide, from which the effective polarizability can be inferred. We present two methods to extract the effective polarizability of a metamaterial element embedded in a one- or two-dimensional waveguide. This is a first step towards a comprehensive, multiscale modeling platform for metasurface antennas-large arrays of metamaterial elements embedded in a waveguide structure that radiates into free-space-in which the detailed electromagnetic responses of metamaterial elements are replaced by polarizable dipoles. We consider the design and modeling of metasurfaces that couple energy from guided waves to propagating wavefronts.

Awa imani couple