Phase analysis for off-specular reflectarray antennas

For reflectarrays radiating in off-specular directions, part of the scattered field may still be directed in the direction of specular reflection. In this paper, it is shown that this specular reflection can be due to a periodic error occurring in the applied phase shift. Usually, this phase shift is calculated using an infinite periodic array analysis, in which all elements are supposed to have the same size and radiate at the same frequency. However, in a reflectarray the size of patches is varying, causing the applied phase to differ from the expected one.