Frequency selective surfaces (FSS) enhanced several applications, contributing significantly to improve the performance of modern communication systems. There are several applications that use FSS, such as, ultra wide band antennas [1], infrared filters [2], radomes [3], reflectarrays and inflatable antennas [4], etc. Besides, it was also observed that the FSS can be used in different bands of the electromagnetic spectrum such as microwave and millimeter wave [5]. Figure 1 illustrates some FSS composed of conducting patch elements spaced with periodicities Tx and Ty in x and y directions, respectively. These patches are printed on a dielectric layer with permittivity εr and thickness h.