Design of a metalens for correcting the phase distortions of a hemispheric dielectric radome in the ka band

Metasheets are ultra-thin sheets built from sub-wavelength resonators designed to achieve certain frequency-dependent transmission behavior. A semianalytical approach based on an equivalent circuit representation is proposed to calculate the microwave transmission through metasheets consisting of two-dimensional periodic arrays of planar circular metal rings on a dielectric substrate. In the semianalytical approach, the impedances of the equivalent circuit are parameterized and fitted to match the values of transmission coefficients obtained by full-wave simulations at selected frequency points. As dimensional parameters, the outer radius and width of the ring are considered. A metalens with four concentric zones is designed by using this semianalytical approach to correct the phase distortions due to a polypropylene hemispheric radome at frequencies around 28 GHz in the Ka band. It is shown that the designed metalens works well for 27 GHz, 28 GHz, 29 GHz, and 29.5 GHz, implying the bandwidth of approximately 2.5 GHz. The field transmitted through the metalens and the radome is calculated by Physical Optics (PO). The electrically large integration area is divided into small square facets to calculate the PO integral. The calculated and measured results are shown to agree well.