Dualband Stacked Metasurface Reflectarray

A reflectarray antenna operating at two distinct frequencies is reported. The antenna consists of two metasurfaces (subwavelength patterned metallic claddings) above a ground plane, separated by dielectric substrates. The metasurfaces are homogenized and the reflectarray is designed using a system of coupled volume-surface integral equations. The system includes three surface integral equations for the currents on the thin metasurfaces and ground plane, and two volume integral equations for the polarization currents within the dielectric substrates. The system of integral equations is discretized using the method of moments and simultaneously solved for the currents and the electric sheet impedances of the metasurfaces needed to collimate an incident cylindrical wave upon reflection at two different frequencies. The system is initially nonlinear as both the currents and the sheet impedances are unknown. A guess and update design procedure is used to linearize the system and solve it iteratively. The performance of the metasurface reflectarray antenna is verified using a commercial finite element solver, validating the design algorithm.