Efficient analysis of multilayered periodic structures with application to the design of reflectarray antennas

Abstract

In order to design reflectarray antennas within reasonable CPU times, fast and accurate numerical tools for the analysis of periodic multilayered structures are required. In this paper the method of moments in the spectral domain (MoM-SD) based on multilayered Green's functions (MGF) is applied to the analysis of periodic structures containing either multilayered stacked patches in the unit cell or coplanar parallel dipoles in the unit cell. These two multiresonant cells are potential elements for the design of reflectarray antennas. In the paper we show that the use of basis functions with edge singularities in the approximation of the current density on the patches/dipoles leads to important computer memory and CPU times savings in the analysis of the periodic structures. Also, a rational fitting technique is introduced which makes it possible to obtain closed-form expressions for the scattering matrix of the periodic structures in terms of the dimension of the patches/dipoles used to adjust the phase of the reflectarray elements. Finally, it is shown that reflectarray antennas made of parallel dipoles and reflectarray antennas made of stacked patches have a similar performance in terms of bandwidth and phase range. However, the former antennas are preferable to the latter since they are simpler to manufacture and cheaper.