Phase Response of Microstrip Reflectarray Elements by FDTD Analysis

The microstrip reflectarray antenna is a microstrip patch element planar array, which reflects the incident fields radiating from a feed antenna. Each patch element introduces a phase change to the scattered fields. In this paper, the scattering of the incident plane wave to a microstrip infinite array which performed by similar microstrip patch elements has been investigated. Determination of the reflected fields phase shift is desired. Finite difference time domain (FDTD) method has been employed to calculate the phase shifts. At first, the infinite array configuration is converted to an equivalent unit cell configuration consisting only one radiator element using PEC and PMC walls around it. Then, a TEM plane wave excitation has been introduced for this equivalent waveguide structure and the reflected fields phase shift is determined by discretization of time domain Maxwell´s equations and applying FDTD method.