Abstract
In this work we investigate three different artificial ground planes for microstrip antenna design, which are useful for different applications. The three different ground plane configurations studied include: (i) conventional dielectric substrate backed by a perfect conductor; (ii) a loop type of artificial magnetic conductor (AMC); and a spiral-type of AMC. Both the loop and spiral types of AMCs tend to lower the resonant frequency of the microstrip patch antenna (MPA), as compared to that of the dielectric substrate, for the linearly polarized case. However, the spiral AMC can be used to realize circular polarization as well, at a different frequency band, hence, is useful for designing dual-band dual-polarization microstrip antennas.