Reflectarray phase errors due to finite patch size

Due to the finite sizes of the patches in the patch array of a microstrip reflectarray, the phase errors attributed to this size factor is generally significant at large subtended feed angles, since a large difference in the phase delay exists across the dimension of each patch. The larger the patch dimension is, the larger the phase error becomes, especially at large subtended feed angles. This will degrade the reflectarray performance. Nevertheless, such phase errors are reduced by increasing the F/D ratios, and by employing small patch dimensions as much as possible.