Effect of extending grounded substrate beyond AMC on the performance of spiral antennas

Abstract

Development of artificial magnetic conductor (AMC) ground planes has resulted in low profile planar antennas. Essentially, AMC structures consist of a periodic array of arbitrarily shaped patches backed by a grounded dielectric slab. Among planar antennas, the spiral antenna is an excellent candidate for circular polarization applications. In [1–5], considerable efforts have been focused on decreasing the overall height of the curl and spiral antennas. Among which, a very compact and low profile spiral antenna was designed with a distance of only 0.02λο in [5], where λο is the free-space wavelength at 4.5GHz.